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	Version: linux-6.0.1 spark-3.0.0 hadoop-3.2.0-src hadoop-3.3.0-src spark-2.4.7 linux-4.15.13 hadoop-2.7.4-src Revert   Change

 // SPDX-License-Identifier: GPL-2.0-only
 /*
  * linux/fs/nfs/pagelist.c
  *
  * A set of helper functions for managing NFS read and write requests.
  * The main purpose of these routines is to provide support for the
  * coalescing of several requests into a single RPC call.
  *
  * Copyright 2000, 2001 (c) Trond Myklebust <trond.myklebust@fys.uio.no>
  *
  */
 
 #include <linux/slab.h>
 #include <linux/file.h>
 #include <linux/sched.h>
 #include <linux/sunrpc/clnt.h>
 #include <linux/nfs.h>
 #include <linux/nfs3.h>
 #include <linux/nfs4.h>
 #include <linux/nfs_fs.h>
 #include <linux/nfs_page.h>
 #include <linux/nfs_mount.h>
 #include <linux/export.h>
 
 #include "internal.h"
 #include "pnfs.h"
 #include "nfstrace.h"
 
 #define NFSDBG_FACILITY     NFSDBG_PAGECACHE
 
 static struct kmem_cache *nfs_page_cachep;
 static const struct rpc_call_ops nfs_pgio_common_ops;
 
 static struct nfs_pgio_mirror *
 nfs_pgio_get_mirror(struct nfs_pageio_descriptor *desc, u32 idx)
 {
     if (desc->pg_ops->pg_get_mirror)
         return desc->pg_ops->pg_get_mirror(desc, idx);
     return &desc->pg_mirrors[0];
 }
 
 struct nfs_pgio_mirror *
 nfs_pgio_current_mirror(struct nfs_pageio_descriptor *desc)
 {
     return nfs_pgio_get_mirror(desc, desc->pg_mirror_idx);
 }
 EXPORT_SYMBOL_GPL(nfs_pgio_current_mirror);
 
 static u32
 nfs_pgio_set_current_mirror(struct nfs_pageio_descriptor *desc, u32 idx)
 {
     if (desc->pg_ops->pg_set_mirror)
         return desc->pg_ops->pg_set_mirror(desc, idx);
     return desc->pg_mirror_idx;
 }
 
 void nfs_pgheader_init(struct nfs_pageio_descriptor *desc,
                struct nfs_pgio_header *hdr,
                void (*release)(struct nfs_pgio_header *hdr))
 {
     struct nfs_pgio_mirror *mirror = nfs_pgio_current_mirror(desc);
 
 
     hdr->req = nfs_list_entry(mirror->pg_list.next);
     hdr->inode = desc->pg_inode;
     hdr->cred = nfs_req_openctx(hdr->req)->cred;
     hdr->io_start = req_offset(hdr->req);
     hdr->good_bytes = mirror->pg_count;
     hdr->io_completion = desc->pg_io_completion;
     hdr->dreq = desc->pg_dreq;
     hdr->release = release;
     hdr->completion_ops = desc->pg_completion_ops;
     if (hdr->completion_ops->init_hdr)
         hdr->completion_ops->init_hdr(hdr);
 
     hdr->pgio_mirror_idx = desc->pg_mirror_idx;
 }
 EXPORT_SYMBOL_GPL(nfs_pgheader_init);
 
 void nfs_set_pgio_error(struct nfs_pgio_header *hdr, int error, loff_t pos)
 {
     unsigned int new = pos - hdr->io_start;
 
     trace_nfs_pgio_error(hdr, error, pos);
     if (hdr->good_bytes > new) {
         hdr->good_bytes = new;
         clear_bit(NFS_IOHDR_EOF, &hdr->flags);
         if (!test_and_set_bit(NFS_IOHDR_ERROR, &hdr->flags))
             hdr->error = error;
     }
 }
 
 static inline struct nfs_page *nfs_page_alloc(void)
 {
     struct nfs_page *p =
         kmem_cache_zalloc(nfs_page_cachep, nfs_io_gfp_mask());
     if (p)
         INIT_LIST_HEAD(&p->wb_list);
     return p;
 }
 
 static inline void
 nfs_page_free(struct nfs_page *p)
 {
     kmem_cache_free(nfs_page_cachep, p);
 }
 
 /**
  * nfs_iocounter_wait - wait for i/o to complete
  * @l_ctx: nfs_lock_context with io_counter to use
  *
  * returns -ERESTARTSYS if interrupted by a fatal signal.
  * Otherwise returns 0 once the io_count hits 0.
  */
 int
 nfs_iocounter_wait(struct nfs_lock_context *l_ctx)
 {
     return wait_var_event_killable(&l_ctx->io_count,
                        !atomic_read(&l_ctx->io_count));
 }
 
 /**
  * nfs_async_iocounter_wait - wait on a rpc_waitqueue for I/O
  * to complete
  * @task: the rpc_task that should wait
  * @l_ctx: nfs_lock_context with io_counter to check
  *
  * Returns true if there is outstanding I/O to wait on and the
  * task has been put to sleep.
  */
 bool
 nfs_async_iocounter_wait(struct rpc_task *task, struct nfs_lock_context *l_ctx)
 {
     struct inode *inode = d_inode(l_ctx->open_context->dentry);
     bool ret = false;
 
     if (atomic_read(&l_ctx->io_count) > 0) {
         rpc_sleep_on(&NFS_SERVER(inode)->uoc_rpcwaitq, task, NULL);
         ret = true;
     }
 
     if (atomic_read(&l_ctx->io_count) == 0) {
         rpc_wake_up_queued_task(&NFS_SERVER(inode)->uoc_rpcwaitq, task);
         ret = false;
     }
 
     return ret;
 }
 EXPORT_SYMBOL_GPL(nfs_async_iocounter_wait);
 
 /*
  * nfs_page_lock_head_request - page lock the head of the page group
  * @req: any member of the page group
  */
 struct nfs_page *
 nfs_page_group_lock_head(struct nfs_page *req)
 {
     struct nfs_page *head = req->wb_head;
 
     while (!nfs_lock_request(head)) {
         int ret = nfs_wait_on_request(head);
         if (ret < 0)
             return ERR_PTR(ret);
     }
     if (head != req)
         kref_get(&head->wb_kref);
     return head;
 }
 
 /*
  * nfs_unroll_locks -  unlock all newly locked reqs and wait on @req
  * @head: head request of page group, must be holding head lock
  * @req: request that couldn't lock and needs to wait on the req bit lock
  *
  * This is a helper function for nfs_lock_and_join_requests
  * returns 0 on success, < 0 on error.
  */
 static void
 nfs_unroll_locks(struct nfs_page *head, struct nfs_page *req)
 {
     struct nfs_page *tmp;
 
     /* relinquish all the locks successfully grabbed this run */
     for (tmp = head->wb_this_page ; tmp != req; tmp = tmp->wb_this_page) {
         if (!kref_read(&tmp->wb_kref))
             continue;
         nfs_unlock_and_release_request(tmp);
     }
 }
 
 /*
  * nfs_page_group_lock_subreq -  try to lock a subrequest
  * @head: head request of page group
  * @subreq: request to lock
  *
  * This is a helper function for nfs_lock_and_join_requests which
  * must be called with the head request and page group both locked.
  * On error, it returns with the page group unlocked.
  */
 static int
 nfs_page_group_lock_subreq(struct nfs_page *head, struct nfs_page *subreq)
 {
     int ret;
 
     if (!kref_get_unless_zero(&subreq->wb_kref))
         return 0;
     while (!nfs_lock_request(subreq)) {
         nfs_page_group_unlock(head);
         ret = nfs_wait_on_request(subreq);
         if (!ret)
             ret = nfs_page_group_lock(head);
         if (ret < 0) {
             nfs_unroll_locks(head, subreq);
             nfs_release_request(subreq);
             return ret;
         }
     }
     return 0;
 }
 
 /*
  * nfs_page_group_lock_subrequests -  try to lock the subrequests
  * @head: head request of page group
  *
  * This is a helper function for nfs_lock_and_join_requests which
  * must be called with the head request locked.
  */
 int nfs_page_group_lock_subrequests(struct nfs_page *head)
 {
     struct nfs_page *subreq;
     int ret;
 
     ret = nfs_page_group_lock(head);
     if (ret < 0)
         return ret;
     /* lock each request in the page group */
     for (subreq = head->wb_this_page; subreq != head;
             subreq = subreq->wb_this_page) {
         ret = nfs_page_group_lock_subreq(head, subreq);
         if (ret < 0)
             return ret;
     }
     nfs_page_group_unlock(head);
     return 0;
 }
 
 /*
  * nfs_page_set_headlock - set the request PG_HEADLOCK
  * @req: request that is to be locked
  *
  * this lock must be held when modifying req->wb_head
  *
  * return 0 on success, < 0 on error
  */
 int
 nfs_page_set_headlock(struct nfs_page *req)
 {
     if (!test_and_set_bit(PG_HEADLOCK, &req->wb_flags))
         return 0;
 
     set_bit(PG_CONTENDED1, &req->wb_flags);
     smp_mb__after_atomic();
     return wait_on_bit_lock(&req->wb_flags, PG_HEADLOCK,
                 TASK_UNINTERRUPTIBLE);
 }
 
 /*
  * nfs_page_clear_headlock - clear the request PG_HEADLOCK
  * @req: request that is to be locked
  */
 void
 nfs_page_clear_headlock(struct nfs_page *req)
 {
     clear_bit_unlock(PG_HEADLOCK, &req->wb_flags);
     smp_mb__after_atomic();
     if (!test_bit(PG_CONTENDED1, &req->wb_flags))
         return;
     wake_up_bit(&req->wb_flags, PG_HEADLOCK);
 }
 
 /*
  * nfs_page_group_lock - lock the head of the page group
  * @req: request in group that is to be locked
  *
  * this lock must be held when traversing or modifying the page
  * group list
  *
  * return 0 on success, < 0 on error
  */
 int
 nfs_page_group_lock(struct nfs_page *req)
 {
     int ret;
 
     ret = nfs_page_set_headlock(req);
     if (ret || req->wb_head == req)
         return ret;
     return nfs_page_set_headlock(req->wb_head);
 }
 
 /*
  * nfs_page_group_unlock - unlock the head of the page group
  * @req: request in group that is to be unlocked
  */
 void
 nfs_page_group_unlock(struct nfs_page *req)
 {
     if (req != req->wb_head)
         nfs_page_clear_headlock(req->wb_head);
     nfs_page_clear_headlock(req);
 }
 
 /*
  * nfs_page_group_sync_on_bit_locked
  *
  * must be called with page group lock held
  */
 static bool
 nfs_page_group_sync_on_bit_locked(struct nfs_page *req, unsigned int bit)
 {
     struct nfs_page *head = req->wb_head;
     struct nfs_page *tmp;
 
     WARN_ON_ONCE(!test_bit(PG_HEADLOCK, &head->wb_flags));
     WARN_ON_ONCE(test_and_set_bit(bit, &req->wb_flags));
 
     tmp = req->wb_this_page;
     while (tmp != req) {
         if (!test_bit(bit, &tmp->wb_flags))
             return false;
         tmp = tmp->wb_this_page;
     }
 
     /* true! reset all bits */
     tmp = req;
     do {
         clear_bit(bit, &tmp->wb_flags);
         tmp = tmp->wb_this_page;
     } while (tmp != req);
 
     return true;
 }
 
 /*
  * nfs_page_group_sync_on_bit - set bit on current request, but only
  *   return true if the bit is set for all requests in page group
  * @req - request in page group
  * @bit - PG_* bit that is used to sync page group
  */
 bool nfs_page_group_sync_on_bit(struct nfs_page *req, unsigned int bit)
 {
     bool ret;
 
     nfs_page_group_lock(req);
     ret = nfs_page_group_sync_on_bit_locked(req, bit);
     nfs_page_group_unlock(req);
 
     return ret;
 }
 
 /*
  * nfs_page_group_init - Initialize the page group linkage for @req
  * @req - a new nfs request
  * @prev - the previous request in page group, or NULL if @req is the first
  *         or only request in the group (the head).
  */
 static inline void
 nfs_page_group_init(struct nfs_page *req, struct nfs_page *prev)
 {
     struct inode *inode;
     WARN_ON_ONCE(prev == req);
 
     if (!prev) {
         /* a head request */
         req->wb_head = req;
         req->wb_this_page = req;
     } else {
         /* a subrequest */
         WARN_ON_ONCE(prev->wb_this_page != prev->wb_head);
         WARN_ON_ONCE(!test_bit(PG_HEADLOCK, &prev->wb_head->wb_flags));
         req->wb_head = prev->wb_head;
         req->wb_this_page = prev->wb_this_page;
         prev->wb_this_page = req;
 
         /* All subrequests take a ref on the head request until
          * nfs_page_group_destroy is called */
         kref_get(&req->wb_head->wb_kref);
 
         /* grab extra ref and bump the request count if head request
          * has extra ref from the write/commit path to handle handoff
          * between write and commit lists. */
         if (test_bit(PG_INODE_REF, &prev->wb_head->wb_flags)) {
             inode = page_file_mapping(req->wb_page)->host;
             set_bit(PG_INODE_REF, &req->wb_flags);
             kref_get(&req->wb_kref);
             atomic_long_inc(&NFS_I(inode)->nrequests);
         }
     }
 }
 
 /*
  * nfs_page_group_destroy - sync the destruction of page groups
  * @req - request that no longer needs the page group
  *
  * releases the page group reference from each member once all
  * members have called this function.
  */
 static void
 nfs_page_group_destroy(struct kref *kref)
 {
     struct nfs_page *req = container_of(kref, struct nfs_page, wb_kref);
     struct nfs_page *head = req->wb_head;
     struct nfs_page *tmp, *next;
 
     if (!nfs_page_group_sync_on_bit(req, PG_TEARDOWN))
         goto out;
 
     tmp = req;
     do {
         next = tmp->wb_this_page;
         /* unlink and free */
         tmp->wb_this_page = tmp;
         tmp->wb_head = tmp;
         nfs_free_request(tmp);
         tmp = next;
     } while (tmp != req);
 out:
     /* subrequests must release the ref on the head request */
     if (head != req)
         nfs_release_request(head);
 }
 
 static struct nfs_page *
 __nfs_create_request(struct nfs_lock_context *l_ctx, struct page *page,
            unsigned int pgbase, unsigned int offset,
            unsigned int count)
 {
     struct nfs_page     *req;
     struct nfs_open_context *ctx = l_ctx->open_context;
 
     if (test_bit(NFS_CONTEXT_BAD, &ctx->flags))
         return ERR_PTR(-EBADF);
     /* try to allocate the request struct */
     req = nfs_page_alloc();
     if (req == NULL)
         return ERR_PTR(-ENOMEM);
 
     req->wb_lock_context = l_ctx;
     refcount_inc(&l_ctx->count);
     atomic_inc(&l_ctx->io_count);
 
     /* Initialize the request struct. Initially, we assume a
      * long write-back delay. This will be adjusted in
      * update_nfs_request below if the region is not locked. */
     req->wb_page    = page;
     if (page) {
         req->wb_index = page_index(page);
         get_page(page);
     }
     req->wb_offset  = offset;
     req->wb_pgbase  = pgbase;
     req->wb_bytes   = count;
     kref_init(&req->wb_kref);
     req->wb_nio = 0;
     return req;
 }
 
 /**
  * nfs_create_request - Create an NFS read/write request.
  * @ctx: open context to use
  * @page: page to write
  * @offset: starting offset within the page for the write
  * @count: number of bytes to read/write
  *
  * The page must be locked by the caller. This makes sure we never
  * create two different requests for the same page.
  * User should ensure it is safe to sleep in this function.
  */
 struct nfs_page *
 nfs_create_request(struct nfs_open_context *ctx, struct page *page,
            unsigned int offset, unsigned int count)
 {
     struct nfs_lock_context *l_ctx = nfs_get_lock_context(ctx);
     struct nfs_page *ret;
 
     if (IS_ERR(l_ctx))
         return ERR_CAST(l_ctx);
     ret = __nfs_create_request(l_ctx, page, offset, offset, count);
     if (!IS_ERR(ret))
         nfs_page_group_init(ret, NULL);
     nfs_put_lock_context(l_ctx);
     return ret;
 }
 
 static struct nfs_page *
 nfs_create_subreq(struct nfs_page *req,
           unsigned int pgbase,
           unsigned int offset,
           unsigned int count)
 {
     struct nfs_page *last;
     struct nfs_page *ret;
 
     ret = __nfs_create_request(req->wb_lock_context, req->wb_page,
             pgbase, offset, count);
     if (!IS_ERR(ret)) {
         /* find the last request */
         for (last = req->wb_head;
              last->wb_this_page != req->wb_head;
              last = last->wb_this_page)
             ;
 
         nfs_lock_request(ret);
         ret->wb_index = req->wb_index;
         nfs_page_group_init(ret, last);
         ret->wb_nio = req->wb_nio;
     }
     return ret;
 }
 
 /**
  * nfs_unlock_request - Unlock request and wake up sleepers.
  * @req: pointer to request
  */
 void nfs_unlock_request(struct nfs_page *req)
 {
     clear_bit_unlock(PG_BUSY, &req->wb_flags);
     smp_mb__after_atomic();
     if (!test_bit(PG_CONTENDED2, &req->wb_flags))
         return;
     wake_up_bit(&req->wb_flags, PG_BUSY);
 }
 
 /**
  * nfs_unlock_and_release_request - Unlock request and release the nfs_page
  * @req: pointer to request
  */
 void nfs_unlock_and_release_request(struct nfs_page *req)
 {
     nfs_unlock_request(req);
     nfs_release_request(req);
 }
 
 /*
  * nfs_clear_request - Free up all resources allocated to the request
  * @req:
  *
  * Release page and open context resources associated with a read/write
  * request after it has completed.
  */
 static void nfs_clear_request(struct nfs_page *req)
 {
     struct page *page = req->wb_page;
     struct nfs_lock_context *l_ctx = req->wb_lock_context;
     struct nfs_open_context *ctx;
 
     if (page != NULL) {
         put_page(page);
         req->wb_page = NULL;
     }
     if (l_ctx != NULL) {
         if (atomic_dec_and_test(&l_ctx->io_count)) {
             wake_up_var(&l_ctx->io_count);
             ctx = l_ctx->open_context;
             if (test_bit(NFS_CONTEXT_UNLOCK, &ctx->flags))
                 rpc_wake_up(&NFS_SERVER(d_inode(ctx->dentry))->uoc_rpcwaitq);
         }
         nfs_put_lock_context(l_ctx);
         req->wb_lock_context = NULL;
     }
 }
 
 /**
  * nfs_free_request - Release the count on an NFS read/write request
  * @req: request to release
  *
  * Note: Should never be called with the spinlock held!
  */
 void nfs_free_request(struct nfs_page *req)
 {
     WARN_ON_ONCE(req->wb_this_page != req);
 
     /* extra debug: make sure no sync bits are still set */
     WARN_ON_ONCE(test_bit(PG_TEARDOWN, &req->wb_flags));
     WARN_ON_ONCE(test_bit(PG_UNLOCKPAGE, &req->wb_flags));
     WARN_ON_ONCE(test_bit(PG_UPTODATE, &req->wb_flags));
     WARN_ON_ONCE(test_bit(PG_WB_END, &req->wb_flags));
     WARN_ON_ONCE(test_bit(PG_REMOVE, &req->wb_flags));
 
     /* Release struct file and open context */
     nfs_clear_request(req);
     nfs_page_free(req);
 }
 
 void nfs_release_request(struct nfs_page *req)
 {
     kref_put(&req->wb_kref, nfs_page_group_destroy);
 }
 EXPORT_SYMBOL_GPL(nfs_release_request);
 
 /**
  * nfs_wait_on_request - Wait for a request to complete.
  * @req: request to wait upon.
  *
  * Interruptible by fatal signals only.
  * The user is responsible for holding a count on the request.
  */
 int
 nfs_wait_on_request(struct nfs_page *req)
 {
     if (!test_bit(PG_BUSY, &req->wb_flags))
         return 0;
     set_bit(PG_CONTENDED2, &req->wb_flags);
     smp_mb__after_atomic();
     return wait_on_bit_io(&req->wb_flags, PG_BUSY,
                   TASK_UNINTERRUPTIBLE);
 }
 EXPORT_SYMBOL_GPL(nfs_wait_on_request);
 
 /*
  * nfs_generic_pg_test - determine if requests can be coalesced
  * @desc: pointer to descriptor
  * @prev: previous request in desc, or NULL
  * @req: this request
  *
  * Returns zero if @req cannot be coalesced into @desc, otherwise it returns
  * the size of the request.
  */
 size_t nfs_generic_pg_test(struct nfs_pageio_descriptor *desc,
                struct nfs_page *prev, struct nfs_page *req)
 {
     struct nfs_pgio_mirror *mirror = nfs_pgio_current_mirror(desc);
 
 
     if (mirror->pg_count > mirror->pg_bsize) {
         /* should never happen */
         WARN_ON_ONCE(1);
         return 0;
     }
 
     /*
      * Limit the request size so that we can still allocate a page array
      * for it without upsetting the slab allocator.
      */
     if (((mirror->pg_count + req->wb_bytes) >> PAGE_SHIFT) *
             sizeof(struct page *) > PAGE_SIZE)
         return 0;
 
     return min(mirror->pg_bsize - mirror->pg_count, (size_t)req->wb_bytes);
 }
 EXPORT_SYMBOL_GPL(nfs_generic_pg_test);
 
 struct nfs_pgio_header *nfs_pgio_header_alloc(const struct nfs_rw_ops *ops)
 {
     struct nfs_pgio_header *hdr = ops->rw_alloc_header();
 
     if (hdr) {
         INIT_LIST_HEAD(&hdr->pages);
         hdr->rw_ops = ops;
     }
     return hdr;
 }
 EXPORT_SYMBOL_GPL(nfs_pgio_header_alloc);
 
 /**
  * nfs_pgio_data_destroy - make @hdr suitable for reuse
  *
  * Frees memory and releases refs from nfs_generic_pgio, so that it may
  * be called again.
  *
  * @hdr: A header that has had nfs_generic_pgio called
  */
 static void nfs_pgio_data_destroy(struct nfs_pgio_header *hdr)
 {
     if (hdr->args.context)
         put_nfs_open_context(hdr->args.context);
     if (hdr->page_array.pagevec != hdr->page_array.page_array)
         kfree(hdr->page_array.pagevec);
 }
 
 /*
  * nfs_pgio_header_free - Free a read or write header
  * @hdr: The header to free
  */
 void nfs_pgio_header_free(struct nfs_pgio_header *hdr)
 {
     nfs_pgio_data_destroy(hdr);
     hdr->rw_ops->rw_free_header(hdr);
 }
 EXPORT_SYMBOL_GPL(nfs_pgio_header_free);
 
 /**
  * nfs_pgio_rpcsetup - Set up arguments for a pageio call
  * @hdr: The pageio hdr
  * @count: Number of bytes to read
  * @how: How to commit data (writes only)
  * @cinfo: Commit information for the call (writes only)
  */
 static void nfs_pgio_rpcsetup(struct nfs_pgio_header *hdr,
                   unsigned int count,
                   int how, struct nfs_commit_info *cinfo)
 {
     struct nfs_page *req = hdr->req;
 
     /* Set up the RPC argument and reply structs
      * NB: take care not to mess about with hdr->commit et al. */
 
     hdr->args.fh     = NFS_FH(hdr->inode);
     hdr->args.offset = req_offset(req);
     /* pnfs_set_layoutcommit needs this */
     hdr->mds_offset = hdr->args.offset;
     hdr->args.pgbase = req->wb_pgbase;
     hdr->args.pages  = hdr->page_array.pagevec;
     hdr->args.count  = count;
     hdr->args.context = get_nfs_open_context(nfs_req_openctx(req));
     hdr->args.lock_context = req->wb_lock_context;
     hdr->args.stable  = NFS_UNSTABLE;
     switch (how & (FLUSH_STABLE | FLUSH_COND_STABLE)) {
     case 0:
         break;
     case FLUSH_COND_STABLE:
         if (nfs_reqs_to_commit(cinfo))
             break;
         fallthrough;
     default:
         hdr->args.stable = NFS_FILE_SYNC;
     }
 
     hdr->res.fattr   = &hdr->fattr;
     hdr->res.count   = 0;
     hdr->res.eof     = 0;
     hdr->res.verf    = &hdr->verf;
     nfs_fattr_init(&hdr->fattr);
 }
 
 /**
  * nfs_pgio_prepare - Prepare pageio hdr to go over the wire
  * @task: The current task
  * @calldata: pageio header to prepare
  */
 static void nfs_pgio_prepare(struct rpc_task *task, void *calldata)
 {
     struct nfs_pgio_header *hdr = calldata;
     int err;
     err = NFS_PROTO(hdr->inode)->pgio_rpc_prepare(task, hdr);
     if (err)
         rpc_exit(task, err);
 }
 
 int nfs_initiate_pgio(struct rpc_clnt *clnt, struct nfs_pgio_header *hdr,
               const struct cred *cred, const struct nfs_rpc_ops *rpc_ops,
               const struct rpc_call_ops *call_ops, int how, int flags)
 {
     struct rpc_task *task;
     struct rpc_message msg = {
         .rpc_argp = &hdr->args,
         .rpc_resp = &hdr->res,
         .rpc_cred = cred,
     };
     struct rpc_task_setup task_setup_data = {
         .rpc_client = clnt,
         .task = &hdr->task,
         .rpc_message = &msg,
         .callback_ops = call_ops,
         .callback_data = hdr,
         .workqueue = nfsiod_workqueue,
         .flags = RPC_TASK_ASYNC | flags,
     };
 
     if (nfs_server_capable(hdr->inode, NFS_CAP_MOVEABLE))
         task_setup_data.flags |= RPC_TASK_MOVEABLE;
 
     hdr->rw_ops->rw_initiate(hdr, &msg, rpc_ops, &task_setup_data, how);
 
     dprintk("NFS: initiated pgio call "
         "(req %s/%llu, %u bytes @ offset %llu)\n",
         hdr->inode->i_sb->s_id,
         (unsigned long long)NFS_FILEID(hdr->inode),
         hdr->args.count,
         (unsigned long long)hdr->args.offset);
 
     task = rpc_run_task(&task_setup_data);
     if (IS_ERR(task))
         return PTR_ERR(task);
     rpc_put_task(task);
     return 0;
 }
 EXPORT_SYMBOL_GPL(nfs_initiate_pgio);
 
 /**
  * nfs_pgio_error - Clean up from a pageio error
  * @hdr: pageio header
  */
 static void nfs_pgio_error(struct nfs_pgio_header *hdr)
 {
     set_bit(NFS_IOHDR_REDO, &hdr->flags);
     hdr->completion_ops->completion(hdr);
 }
 
 /**
  * nfs_pgio_release - Release pageio data
  * @calldata: The pageio header to release
  */
 static void nfs_pgio_release(void *calldata)
 {
     struct nfs_pgio_header *hdr = calldata;
     hdr->completion_ops->completion(hdr);
 }
 
 static void nfs_pageio_mirror_init(struct nfs_pgio_mirror *mirror,
                    unsigned int bsize)
 {
     INIT_LIST_HEAD(&mirror->pg_list);
     mirror->pg_bytes_written = 0;
     mirror->pg_count = 0;
     mirror->pg_bsize = bsize;
     mirror->pg_base = 0;
     mirror->pg_recoalesce = 0;
 }
 
 /**
  * nfs_pageio_init - initialise a page io descriptor
  * @desc: pointer to descriptor
  * @inode: pointer to inode
  * @pg_ops: pointer to pageio operations
  * @compl_ops: pointer to pageio completion operations
  * @rw_ops: pointer to nfs read/write operations
  * @bsize: io block size
  * @io_flags: extra parameters for the io function
  */
 void nfs_pageio_init(struct nfs_pageio_descriptor *desc,
              struct inode *inode,
              const struct nfs_pageio_ops *pg_ops,
              const struct nfs_pgio_completion_ops *compl_ops,
              const struct nfs_rw_ops *rw_ops,
              size_t bsize,
              int io_flags)
 {
     desc->pg_moreio = 0;
     desc->pg_inode = inode;
     desc->pg_ops = pg_ops;
     desc->pg_completion_ops = compl_ops;
     desc->pg_rw_ops = rw_ops;
     desc->pg_ioflags = io_flags;
     desc->pg_error = 0;
     desc->pg_lseg = NULL;
     desc->pg_io_completion = NULL;
     desc->pg_dreq = NULL;
     desc->pg_bsize = bsize;
 
     desc->pg_mirror_count = 1;
     desc->pg_mirror_idx = 0;
 
     desc->pg_mirrors_dynamic = NULL;
     desc->pg_mirrors = desc->pg_mirrors_static;
     nfs_pageio_mirror_init(&desc->pg_mirrors[0], bsize);
     desc->pg_maxretrans = 0;
 }
 
 /**
  * nfs_pgio_result - Basic pageio error handling
  * @task: The task that ran
  * @calldata: Pageio header to check
  */
 static void nfs_pgio_result(struct rpc_task *task, void *calldata)
 {
     struct nfs_pgio_header *hdr = calldata;
     struct inode *inode = hdr->inode;
 
     if (hdr->rw_ops->rw_done(task, hdr, inode) != 0)
         return;
     if (task->tk_status < 0)
         nfs_set_pgio_error(hdr, task->tk_status, hdr->args.offset);
     else
         hdr->rw_ops->rw_result(task, hdr);
 }
 
 /*
  * Create an RPC task for the given read or write request and kick it.
  * The page must have been locked by the caller.
  *
  * It may happen that the page we're passed is not marked dirty.
  * This is the case if nfs_updatepage detects a conflicting request
  * that has been written but not committed.
  */
 int nfs_generic_pgio(struct nfs_pageio_descriptor *desc,
              struct nfs_pgio_header *hdr)
 {
     struct nfs_pgio_mirror *mirror = nfs_pgio_current_mirror(desc);
 
     struct nfs_page     *req;
     struct page     **pages,
                 *last_page;
     struct list_head *head = &mirror->pg_list;
     struct nfs_commit_info cinfo;
     struct nfs_page_array *pg_array = &hdr->page_array;
     unsigned int pagecount, pageused;
     gfp_t gfp_flags = nfs_io_gfp_mask();
 
     pagecount = nfs_page_array_len(mirror->pg_base, mirror->pg_count);
     pg_array->npages = pagecount;
 
     if (pagecount <= ARRAY_SIZE(pg_array->page_array))
         pg_array->pagevec = pg_array->page_array;
     else {
         pg_array->pagevec = kcalloc(pagecount, sizeof(struct page *), gfp_flags);
         if (!pg_array->pagevec) {
             pg_array->npages = 0;
             nfs_pgio_error(hdr);
             desc->pg_error = -ENOMEM;
             return desc->pg_error;
         }
     }
 
     nfs_init_cinfo(&cinfo, desc->pg_inode, desc->pg_dreq);
     pages = hdr->page_array.pagevec;
     last_page = NULL;
     pageused = 0;
     while (!list_empty(head)) {
         req = nfs_list_entry(head->next);
         nfs_list_move_request(req, &hdr->pages);
 
         if (!last_page || last_page != req->wb_page) {
             pageused++;
             if (pageused > pagecount)
                 break;
             *pages++ = last_page = req->wb_page;
         }
     }
     if (WARN_ON_ONCE(pageused != pagecount)) {
         nfs_pgio_error(hdr);
         desc->pg_error = -EINVAL;
         return desc->pg_error;
     }
 
     if ((desc->pg_ioflags & FLUSH_COND_STABLE) &&
         (desc->pg_moreio || nfs_reqs_to_commit(&cinfo)))
         desc->pg_ioflags &= ~FLUSH_COND_STABLE;
 
     /* Set up the argument struct */
     nfs_pgio_rpcsetup(hdr, mirror->pg_count, desc->pg_ioflags, &cinfo);
     desc->pg_rpc_callops = &nfs_pgio_common_ops;
     return 0;
 }
 EXPORT_SYMBOL_GPL(nfs_generic_pgio);
 
 static int nfs_generic_pg_pgios(struct nfs_pageio_descriptor *desc)
 {
     struct nfs_pgio_header *hdr;
     int ret;
     unsigned short task_flags = 0;
 
     hdr = nfs_pgio_header_alloc(desc->pg_rw_ops);
     if (!hdr) {
         desc->pg_error = -ENOMEM;
         return desc->pg_error;
     }
     nfs_pgheader_init(desc, hdr, nfs_pgio_header_free);
     ret = nfs_generic_pgio(desc, hdr);
     if (ret == 0) {
         if (NFS_SERVER(hdr->inode)->nfs_client->cl_minorversion)
             task_flags = RPC_TASK_MOVEABLE;
         ret = nfs_initiate_pgio(NFS_CLIENT(hdr->inode),
                     hdr,
                     hdr->cred,
                     NFS_PROTO(hdr->inode),
                     desc->pg_rpc_callops,
                     desc->pg_ioflags,
                     RPC_TASK_CRED_NOREF | task_flags);
     }
     return ret;
 }
 
 static struct nfs_pgio_mirror *
 nfs_pageio_alloc_mirrors(struct nfs_pageio_descriptor *desc,
         unsigned int mirror_count)
 {
     struct nfs_pgio_mirror *ret;
     unsigned int i;
 
     kfree(desc->pg_mirrors_dynamic);
     desc->pg_mirrors_dynamic = NULL;
     if (mirror_count == 1)
         return desc->pg_mirrors_static;
     ret = kmalloc_array(mirror_count, sizeof(*ret), nfs_io_gfp_mask());
     if (ret != NULL) {
         for (i = 0; i < mirror_count; i++)
             nfs_pageio_mirror_init(&ret[i], desc->pg_bsize);
         desc->pg_mirrors_dynamic = ret;
     }
     return ret;
 }
 
 /*
  * nfs_pageio_setup_mirroring - determine if mirroring is to be used
  *              by calling the pg_get_mirror_count op
  */
 static void nfs_pageio_setup_mirroring(struct nfs_pageio_descriptor *pgio,
                        struct nfs_page *req)
 {
     unsigned int mirror_count = 1;
 
     if (pgio->pg_ops->pg_get_mirror_count)
         mirror_count = pgio->pg_ops->pg_get_mirror_count(pgio, req);
     if (mirror_count == pgio->pg_mirror_count || pgio->pg_error < 0)
         return;
 
     if (!mirror_count || mirror_count > NFS_PAGEIO_DESCRIPTOR_MIRROR_MAX) {
         pgio->pg_error = -EINVAL;
         return;
     }
 
     pgio->pg_mirrors = nfs_pageio_alloc_mirrors(pgio, mirror_count);
     if (pgio->pg_mirrors == NULL) {
         pgio->pg_error = -ENOMEM;
         pgio->pg_mirrors = pgio->pg_mirrors_static;
         mirror_count = 1;
     }
     pgio->pg_mirror_count = mirror_count;
 }
 
 static void nfs_pageio_cleanup_mirroring(struct nfs_pageio_descriptor *pgio)
 {
     pgio->pg_mirror_count = 1;
     pgio->pg_mirror_idx = 0;
     pgio->pg_mirrors = pgio->pg_mirrors_static;
     kfree(pgio->pg_mirrors_dynamic);
     pgio->pg_mirrors_dynamic = NULL;
 }
 
 static bool nfs_match_lock_context(const struct nfs_lock_context *l1,
         const struct nfs_lock_context *l2)
 {
     return l1->lockowner == l2->lockowner;
 }
 
 /**
  * nfs_coalesce_size - test two requests for compatibility
  * @prev: pointer to nfs_page
  * @req: pointer to nfs_page
  * @pgio: pointer to nfs_pagio_descriptor
  *
  * The nfs_page structures 'prev' and 'req' are compared to ensure that the
  * page data area they describe is contiguous, and that their RPC
  * credentials, NFSv4 open state, and lockowners are the same.
  *
  * Returns size of the request that can be coalesced
  */
 static unsigned int nfs_coalesce_size(struct nfs_page *prev,
                       struct nfs_page *req,
                       struct nfs_pageio_descriptor *pgio)
 {
     struct file_lock_context *flctx;
 
     if (prev) {
         if (!nfs_match_open_context(nfs_req_openctx(req), nfs_req_openctx(prev)))
             return 0;
         flctx = d_inode(nfs_req_openctx(req)->dentry)->i_flctx;
         if (flctx != NULL &&
             !(list_empty_careful(&flctx->flc_posix) &&
               list_empty_careful(&flctx->flc_flock)) &&
             !nfs_match_lock_context(req->wb_lock_context,
                         prev->wb_lock_context))
             return 0;
         if (req_offset(req) != req_offset(prev) + prev->wb_bytes)
             return 0;
         if (req->wb_page == prev->wb_page) {
             if (req->wb_pgbase != prev->wb_pgbase + prev->wb_bytes)
                 return 0;
         } else {
             if (req->wb_pgbase != 0 ||
                 prev->wb_pgbase + prev->wb_bytes != PAGE_SIZE)
                 return 0;
         }
     }
     return pgio->pg_ops->pg_test(pgio, prev, req);
 }
 
 /**
  * nfs_pageio_do_add_request - Attempt to coalesce a request into a page list.
  * @desc: destination io descriptor
  * @req: request
  *
  * If the request 'req' was successfully coalesced into the existing list
  * of pages 'desc', it returns the size of req.
  */
 static unsigned int
 nfs_pageio_do_add_request(struct nfs_pageio_descriptor *desc,
         struct nfs_page *req)
 {
     struct nfs_pgio_mirror *mirror = nfs_pgio_current_mirror(desc);
     struct nfs_page *prev = NULL;
     unsigned int size;
 
     if (list_empty(&mirror->pg_list)) {
         if (desc->pg_ops->pg_init)
             desc->pg_ops->pg_init(desc, req);
         if (desc->pg_error < 0)
             return 0;
         mirror->pg_base = req->wb_pgbase;
         mirror->pg_count = 0;
         mirror->pg_recoalesce = 0;
     } else
         prev = nfs_list_entry(mirror->pg_list.prev);
 
     if (desc->pg_maxretrans && req->wb_nio > desc->pg_maxretrans) {
         if (NFS_SERVER(desc->pg_inode)->flags & NFS_MOUNT_SOFTERR)
             desc->pg_error = -ETIMEDOUT;
         else
             desc->pg_error = -EIO;
         return 0;
     }
 
     size = nfs_coalesce_size(prev, req, desc);
     if (size < req->wb_bytes)
         return size;
     nfs_list_move_request(req, &mirror->pg_list);
     mirror->pg_count += req->wb_bytes;
     return req->wb_bytes;
 }
 
 /*
  * Helper for nfs_pageio_add_request and nfs_pageio_complete
  */
 static void nfs_pageio_doio(struct nfs_pageio_descriptor *desc)
 {
     struct nfs_pgio_mirror *mirror = nfs_pgio_current_mirror(desc);
 
     if (!list_empty(&mirror->pg_list)) {
         int error = desc->pg_ops->pg_doio(desc);
         if (error < 0)
             desc->pg_error = error;
         if (list_empty(&mirror->pg_list))
             mirror->pg_bytes_written += mirror->pg_count;
     }
 }
 
 static void
 nfs_pageio_cleanup_request(struct nfs_pageio_descriptor *desc,
         struct nfs_page *req)
 {
     LIST_HEAD(head);
 
     nfs_list_move_request(req, &head);
     desc->pg_completion_ops->error_cleanup(&head, desc->pg_error);
 }
 
 /**
  * __nfs_pageio_add_request - Attempt to coalesce a request into a page list.
  * @desc: destination io descriptor
  * @req: request
  *
  * This may split a request into subrequests which are all part of the
  * same page group. If so, it will submit @req as the last one, to ensure
  * the pointer to @req is still valid in case of failure.
  *
  * Returns true if the request 'req' was successfully coalesced into the
  * existing list of pages 'desc'.
  */
 static int __nfs_pageio_add_request(struct nfs_pageio_descriptor *desc,
                struct nfs_page *req)
 {
     struct nfs_pgio_mirror *mirror = nfs_pgio_current_mirror(desc);
     struct nfs_page *subreq;
     unsigned int size, subreq_size;
 
     nfs_page_group_lock(req);
 
     subreq = req;
     subreq_size = subreq->wb_bytes;
     for(;;) {
         size = nfs_pageio_do_add_request(desc, subreq);
         if (size == subreq_size) {
             /* We successfully submitted a request */
             if (subreq == req)
                 break;
             req->wb_pgbase += size;
             req->wb_bytes -= size;
             req->wb_offset += size;
             subreq_size = req->wb_bytes;
             subreq = req;
             continue;
         }
         if (WARN_ON_ONCE(subreq != req)) {
             nfs_page_group_unlock(req);
             nfs_pageio_cleanup_request(desc, subreq);
             subreq = req;
             subreq_size = req->wb_bytes;
             nfs_page_group_lock(req);
         }
         if (!size) {
             /* Can't coalesce any more, so do I/O */
             nfs_page_group_unlock(req);
             desc->pg_moreio = 1;
             nfs_pageio_doio(desc);
             if (desc->pg_error < 0 || mirror->pg_recoalesce)
                 return 0;
             /* retry add_request for this subreq */
             nfs_page_group_lock(req);
             continue;
         }
         subreq = nfs_create_subreq(req, req->wb_pgbase,
                 req->wb_offset, size);
         if (IS_ERR(subreq))
             goto err_ptr;
         subreq_size = size;
     }
 
     nfs_page_group_unlock(req);
     return 1;
 err_ptr:
     desc->pg_error = PTR_ERR(subreq);
     nfs_page_group_unlock(req);
     return 0;
 }
 
 static int nfs_do_recoalesce(struct nfs_pageio_descriptor *desc)
 {
     struct nfs_pgio_mirror *mirror = nfs_pgio_current_mirror(desc);
     LIST_HEAD(head);
 
     do {
         list_splice_init(&mirror->pg_list, &head);
         mirror->pg_recoalesce = 0;
 
         while (!list_empty(&head)) {
             struct nfs_page *req;
 
             req = list_first_entry(&head, struct nfs_page, wb_list);
             if (__nfs_pageio_add_request(desc, req))
                 continue;
             if (desc->pg_error < 0) {
                 list_splice_tail(&head, &mirror->pg_list);
                 mirror->pg_recoalesce = 1;
                 return 0;
             }
             break;
         }
     } while (mirror->pg_recoalesce);
     return 1;
 }
 
 static int nfs_pageio_add_request_mirror(struct nfs_pageio_descriptor *desc,
         struct nfs_page *req)
 {
     int ret;
 
     do {
         ret = __nfs_pageio_add_request(desc, req);
         if (ret)
             break;
         if (desc->pg_error < 0)
             break;
         ret = nfs_do_recoalesce(desc);
     } while (ret);
 
     return ret;
 }
 
 static void nfs_pageio_error_cleanup(struct nfs_pageio_descriptor *desc)
 {
     u32 midx;
     struct nfs_pgio_mirror *mirror;
 
     if (!desc->pg_error)
         return;
 
     for (midx = 0; midx < desc->pg_mirror_count; midx++) {
         mirror = nfs_pgio_get_mirror(desc, midx);
         desc->pg_completion_ops->error_cleanup(&mirror->pg_list,
                 desc->pg_error);
     }
 }
 
 int nfs_pageio_add_request(struct nfs_pageio_descriptor *desc,
                struct nfs_page *req)
 {
     u32 midx;
     unsigned int pgbase, offset, bytes;
     struct nfs_page *dupreq;
 
     pgbase = req->wb_pgbase;
     offset = req->wb_offset;
     bytes = req->wb_bytes;
 
     nfs_pageio_setup_mirroring(desc, req);
     if (desc->pg_error < 0)
         goto out_failed;
 
     /* Create the mirror instances first, and fire them off */
     for (midx = 1; midx < desc->pg_mirror_count; midx++) {
         nfs_page_group_lock(req);
 
         dupreq = nfs_create_subreq(req,
                 pgbase, offset, bytes);
 
         nfs_page_group_unlock(req);
         if (IS_ERR(dupreq)) {
             desc->pg_error = PTR_ERR(dupreq);
             goto out_failed;
         }
 
         nfs_pgio_set_current_mirror(desc, midx);
         if (!nfs_pageio_add_request_mirror(desc, dupreq))
             goto out_cleanup_subreq;
     }
 
     nfs_pgio_set_current_mirror(desc, 0);
     if (!nfs_pageio_add_request_mirror(desc, req))
         goto out_failed;
 
     return 1;
 
 out_cleanup_subreq:
     nfs_pageio_cleanup_request(desc, dupreq);
 out_failed:
     nfs_pageio_error_cleanup(desc);
     return 0;
 }
 
 /*
  * nfs_pageio_complete_mirror - Complete I/O on the current mirror of an
  *              nfs_pageio_descriptor
  * @desc: pointer to io descriptor
  * @mirror_idx: pointer to mirror index
  */
 static void nfs_pageio_complete_mirror(struct nfs_pageio_descriptor *desc,
                        u32 mirror_idx)
 {
     struct nfs_pgio_mirror *mirror;
     u32 restore_idx;
 
     restore_idx = nfs_pgio_set_current_mirror(desc, mirror_idx);
     mirror = nfs_pgio_current_mirror(desc);
 
     for (;;) {
         nfs_pageio_doio(desc);
         if (desc->pg_error < 0 || !mirror->pg_recoalesce)
             break;
         if (!nfs_do_recoalesce(desc))
             break;
     }
     nfs_pgio_set_current_mirror(desc, restore_idx);
 }
 
 /*
  * nfs_pageio_resend - Transfer requests to new descriptor and resend
  * @hdr - the pgio header to move request from
  * @desc - the pageio descriptor to add requests to
  *
  * Try to move each request (nfs_page) from @hdr to @desc then attempt
  * to send them.
  *
  * Returns 0 on success and < 0 on error.
  */
 int nfs_pageio_resend(struct nfs_pageio_descriptor *desc,
               struct nfs_pgio_header *hdr)
 {
     LIST_HEAD(pages);
 
     desc->pg_io_completion = hdr->io_completion;
     desc->pg_dreq = hdr->dreq;
     list_splice_init(&hdr->pages, &pages);
     while (!list_empty(&pages)) {
         struct nfs_page *req = nfs_list_entry(pages.next);
 
         if (!nfs_pageio_add_request(desc, req))
             break;
     }
     nfs_pageio_complete(desc);
     if (!list_empty(&pages)) {
         int err = desc->pg_error < 0 ? desc->pg_error : -EIO;
         hdr->completion_ops->error_cleanup(&pages, err);
         nfs_set_pgio_error(hdr, err, hdr->io_start);
         return err;
     }
     return 0;
 }
 EXPORT_SYMBOL_GPL(nfs_pageio_resend);
 
 /**
  * nfs_pageio_complete - Complete I/O then cleanup an nfs_pageio_descriptor
  * @desc: pointer to io descriptor
  */
 void nfs_pageio_complete(struct nfs_pageio_descriptor *desc)
 {
     u32 midx;
 
     for (midx = 0; midx < desc->pg_mirror_count; midx++)
         nfs_pageio_complete_mirror(desc, midx);
 
     if (desc->pg_error < 0)
         nfs_pageio_error_cleanup(desc);
     if (desc->pg_ops->pg_cleanup)
         desc->pg_ops->pg_cleanup(desc);
     nfs_pageio_cleanup_mirroring(desc);
 }
 
 /**
  * nfs_pageio_cond_complete - Conditional I/O completion
  * @desc: pointer to io descriptor
  * @index: page index
  *
  * It is important to ensure that processes don't try to take locks
  * on non-contiguous ranges of pages as that might deadlock. This
  * function should be called before attempting to wait on a locked
  * nfs_page. It will complete the I/O if the page index 'index'
  * is not contiguous with the existing list of pages in 'desc'.
  */
 void nfs_pageio_cond_complete(struct nfs_pageio_descriptor *desc, pgoff_t index)
 {
     struct nfs_pgio_mirror *mirror;
     struct nfs_page *prev;
     u32 midx;
 
     for (midx = 0; midx < desc->pg_mirror_count; midx++) {
         mirror = nfs_pgio_get_mirror(desc, midx);
         if (!list_empty(&mirror->pg_list)) {
             prev = nfs_list_entry(mirror->pg_list.prev);
             if (index != prev->wb_index + 1) {
                 nfs_pageio_complete(desc);
                 break;
             }
         }
     }
 }
 
 /*
  * nfs_pageio_stop_mirroring - stop using mirroring (set mirror count to 1)
  */
 void nfs_pageio_stop_mirroring(struct nfs_pageio_descriptor *pgio)
 {
     nfs_pageio_complete(pgio);
 }
 
 int __init nfs_init_nfspagecache(void)
 {
     nfs_page_cachep = kmem_cache_create("nfs_page",
                         sizeof(struct nfs_page),
                         0, SLAB_HWCACHE_ALIGN,
                         NULL);
     if (nfs_page_cachep == NULL)
         return -ENOMEM;
 
     return 0;
 }
 
 void nfs_destroy_nfspagecache(void)
 {
     kmem_cache_destroy(nfs_page_cachep);
 }
 
 static const struct rpc_call_ops nfs_pgio_common_ops = {
     .rpc_call_prepare = nfs_pgio_prepare,
     .rpc_call_done = nfs_pgio_result,
     .rpc_release = nfs_pgio_release,
 };
 
 const struct nfs_pageio_ops nfs_pgio_rw_ops = {
     .pg_test = nfs_generic_pg_test,
     .pg_doio = nfs_generic_pg_pgios,
 };

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