From c63c7b051395368573779c8309aa5c990dcf2f96 Mon Sep 17 00:00:00 2001 From: Trond Myklebust Date: Mon, 2 Apr 2007 19:29:52 -0400 Subject: NFS: Fix a race when doing NFS write coalescing Currently we do write coalescing in a very inefficient manner: one pass in generic_writepages() in order to lock the pages for writing, then one pass in nfs_flush_mapping() and/or nfs_sync_mapping_wait() in order to gather the locked pages for coalescing into RPC requests of size "wsize". In fact, it turns out there is actually a deadlock possible here since we only start I/O on the second pass. If the user signals the process while we're in nfs_sync_mapping_wait(), for instance, then we may exit before starting I/O on all the requests that have been queued up. Signed-off-by: Trond Myklebust --- fs/nfs/pagelist.c | 92 ------------------------------------------------------- 1 file changed, 92 deletions(-) (limited to 'fs/nfs/pagelist.c') diff --git a/fs/nfs/pagelist.c b/fs/nfs/pagelist.c index 094537ddd344..ea1a85df9ab1 100644 --- a/fs/nfs/pagelist.c +++ b/fs/nfs/pagelist.c @@ -17,7 +17,6 @@ #include #include #include -#include #define NFS_PARANOIA 1 @@ -353,25 +352,6 @@ int nfs_pageio_add_request(struct nfs_pageio_descriptor *desc, return 1; } -/** - * nfs_pageio_add_list - Split coalesced requests out from a list. - * @desc: destination io descriptor - * @head: source list - * - * Moves a maximum of 'nmax' elements from one list to another. - * The elements are checked to ensure that they form a contiguous set - * of pages, and that the RPC credentials are the same. - */ -void nfs_pageio_add_list(struct nfs_pageio_descriptor *desc, - struct list_head *head) -{ - while (!list_empty(head)) { - struct nfs_page *req = nfs_list_entry(head->next); - if (!nfs_pageio_add_request(desc, req)) - break; - } -} - /** * nfs_pageio_complete - Complete I/O on an nfs_pageio_descriptor * @desc: pointer to io descriptor @@ -382,78 +362,6 @@ void nfs_pageio_complete(struct nfs_pageio_descriptor *desc) } #define NFS_SCAN_MAXENTRIES 16 -/** - * nfs_scan_dirty - Scan the radix tree for dirty requests - * @mapping: pointer to address space - * @wbc: writeback_control structure - * @dst: Destination list - * - * Moves elements from one of the inode request lists. - * If the number of requests is set to 0, the entire address_space - * starting at index idx_start, is scanned. - * The requests are *not* checked to ensure that they form a contiguous set. - * You must be holding the inode's req_lock when calling this function - */ -long nfs_scan_dirty(struct address_space *mapping, - struct writeback_control *wbc, - struct list_head *dst) -{ - struct nfs_inode *nfsi = NFS_I(mapping->host); - struct nfs_page *pgvec[NFS_SCAN_MAXENTRIES]; - struct nfs_page *req; - pgoff_t idx_start, idx_end; - long res = 0; - int found, i; - - if (nfsi->ndirty == 0) - return 0; - if (wbc->range_cyclic) { - idx_start = 0; - idx_end = ULONG_MAX; - } else if (wbc->range_end == 0) { - idx_start = wbc->range_start >> PAGE_CACHE_SHIFT; - idx_end = ULONG_MAX; - } else { - idx_start = wbc->range_start >> PAGE_CACHE_SHIFT; - idx_end = wbc->range_end >> PAGE_CACHE_SHIFT; - } - - for (;;) { - unsigned int toscan = NFS_SCAN_MAXENTRIES; - - found = radix_tree_gang_lookup_tag(&nfsi->nfs_page_tree, - (void **)&pgvec[0], idx_start, toscan, - NFS_PAGE_TAG_DIRTY); - - /* Did we make progress? */ - if (found <= 0) - break; - - for (i = 0; i < found; i++) { - req = pgvec[i]; - if (!wbc->range_cyclic && req->wb_index > idx_end) - goto out; - - /* Try to lock request and mark it for writeback */ - if (!nfs_set_page_writeback_locked(req)) - goto next; - radix_tree_tag_clear(&nfsi->nfs_page_tree, - req->wb_index, NFS_PAGE_TAG_DIRTY); - nfsi->ndirty--; - nfs_list_remove_request(req); - nfs_list_add_request(req, dst); - res++; - if (res == LONG_MAX) - goto out; -next: - idx_start = req->wb_index + 1; - } - } -out: - WARN_ON ((nfsi->ndirty == 0) != list_empty(&nfsi->dirty)); - return res; -} - /** * nfs_scan_list - Scan a list for matching requests * @nfsi: NFS inode -- cgit v1.2.3