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2021-12-29netfs: fix parameter of cleanup()Jeffle Xu1-3/+3
commit 3cfef1b612e15a0c2f5b1c9d3f3f31ad72d56fcd upstream. The order of these two parameters is just reversed. gcc didn't warn on that, probably because 'void *' can be converted from or to other pointer types without warning. Cc: stable@vger.kernel.org Fixes: 3d3c95046742 ("netfs: Provide readahead and readpage netfs helpers") Fixes: e1b1240c1ff5 ("netfs: Add write_begin helper") Signed-off-by: Jeffle Xu <jefflexu@linux.alibaba.com> Signed-off-by: David Howells <dhowells@redhat.com> Reviewed-by: Jeff Layton <jlayton@redhat.com> Link: https://lore.kernel.org/r/20211207031449.100510-1-jefflexu@linux.alibaba.com/ # v1 Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2021-12-17netfs: Fix lockdep warning from taking sb_writers whilst holding mmap_lockDavid Howells1-10/+5
[ Upstream commit 598ad0bd09329818ee041cb3e4b60ba0a70cb1ee ] Taking sb_writers whilst holding mmap_lock isn't allowed and will result in a lockdep warning like that below. The problem comes from cachefiles needing to take the sb_writers lock in order to do a write to the cache, but being asked to do this by netfslib called from readpage, readahead or write_begin[1]. Fix this by always offloading the write to the cache off to a worker thread. The main thread doesn't need to wait for it, so deadlock can be avoided. This can be tested by running the quick xfstests on something like afs or ceph with lockdep enabled. WARNING: possible circular locking dependency detected 5.15.0-rc1-build2+ #292 Not tainted ------------------------------------------------------ holetest/65517 is trying to acquire lock: ffff88810c81d730 (mapping.invalidate_lock#3){.+.+}-{3:3}, at: filemap_fault+0x276/0x7a5 but task is already holding lock: ffff8881595b53e8 (&mm->mmap_lock#2){++++}-{3:3}, at: do_user_addr_fault+0x28d/0x59c which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #2 (&mm->mmap_lock#2){++++}-{3:3}: validate_chain+0x3c4/0x4a8 __lock_acquire+0x89d/0x949 lock_acquire+0x2dc/0x34b __might_fault+0x87/0xb1 strncpy_from_user+0x25/0x18c removexattr+0x7c/0xe5 __do_sys_fremovexattr+0x73/0x96 do_syscall_64+0x67/0x7a entry_SYSCALL_64_after_hwframe+0x44/0xae -> #1 (sb_writers#10){.+.+}-{0:0}: validate_chain+0x3c4/0x4a8 __lock_acquire+0x89d/0x949 lock_acquire+0x2dc/0x34b cachefiles_write+0x2b3/0x4bb netfs_rreq_do_write_to_cache+0x3b5/0x432 netfs_readpage+0x2de/0x39d filemap_read_page+0x51/0x94 filemap_get_pages+0x26f/0x413 filemap_read+0x182/0x427 new_sync_read+0xf0/0x161 vfs_read+0x118/0x16e ksys_read+0xb8/0x12e do_syscall_64+0x67/0x7a entry_SYSCALL_64_after_hwframe+0x44/0xae -> #0 (mapping.invalidate_lock#3){.+.+}-{3:3}: check_noncircular+0xe4/0x129 check_prev_add+0x16b/0x3a4 validate_chain+0x3c4/0x4a8 __lock_acquire+0x89d/0x949 lock_acquire+0x2dc/0x34b down_read+0x40/0x4a filemap_fault+0x276/0x7a5 __do_fault+0x96/0xbf do_fault+0x262/0x35a __handle_mm_fault+0x171/0x1b5 handle_mm_fault+0x12a/0x233 do_user_addr_fault+0x3d2/0x59c exc_page_fault+0x85/0xa5 asm_exc_page_fault+0x1e/0x30 other info that might help us debug this: Chain exists of: mapping.invalidate_lock#3 --> sb_writers#10 --> &mm->mmap_lock#2 Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(&mm->mmap_lock#2); lock(sb_writers#10); lock(&mm->mmap_lock#2); lock(mapping.invalidate_lock#3); *** DEADLOCK *** 1 lock held by holetest/65517: #0: ffff8881595b53e8 (&mm->mmap_lock#2){++++}-{3:3}, at: do_user_addr_fault+0x28d/0x59c stack backtrace: CPU: 0 PID: 65517 Comm: holetest Not tainted 5.15.0-rc1-build2+ #292 Hardware name: ASUS All Series/H97-PLUS, BIOS 2306 10/09/2014 Call Trace: dump_stack_lvl+0x45/0x59 check_noncircular+0xe4/0x129 ? print_circular_bug+0x207/0x207 ? validate_chain+0x461/0x4a8 ? add_chain_block+0x88/0xd9 ? hlist_add_head_rcu+0x49/0x53 check_prev_add+0x16b/0x3a4 validate_chain+0x3c4/0x4a8 ? check_prev_add+0x3a4/0x3a4 ? mark_lock+0xa5/0x1c6 __lock_acquire+0x89d/0x949 lock_acquire+0x2dc/0x34b ? filemap_fault+0x276/0x7a5 ? rcu_read_unlock+0x59/0x59 ? add_to_page_cache_lru+0x13c/0x13c ? lock_is_held_type+0x7b/0xd3 down_read+0x40/0x4a ? filemap_fault+0x276/0x7a5 filemap_fault+0x276/0x7a5 ? pagecache_get_page+0x2dd/0x2dd ? __lock_acquire+0x8bc/0x949 ? pte_offset_kernel.isra.0+0x6d/0xc3 __do_fault+0x96/0xbf ? do_fault+0x124/0x35a do_fault+0x262/0x35a ? handle_pte_fault+0x1c1/0x20d __handle_mm_fault+0x171/0x1b5 ? handle_pte_fault+0x20d/0x20d ? __lock_release+0x151/0x254 ? mark_held_locks+0x1f/0x78 ? rcu_read_unlock+0x3a/0x59 handle_mm_fault+0x12a/0x233 do_user_addr_fault+0x3d2/0x59c ? pgtable_bad+0x70/0x70 ? rcu_read_lock_bh_held+0xab/0xab exc_page_fault+0x85/0xa5 ? asm_exc_page_fault+0x8/0x30 asm_exc_page_fault+0x1e/0x30 RIP: 0033:0x40192f Code: ff 48 89 c3 48 8b 05 50 28 00 00 48 85 ed 7e 23 31 d2 4b 8d 0c 2f eb 0a 0f 1f 00 48 8b 05 39 28 00 00 48 0f af c2 48 83 c2 01 <48> 89 1c 01 48 39 d5 7f e8 8b 0d f2 27 00 00 31 c0 85 c9 74 0e 8b RSP: 002b:00007f9931867eb0 EFLAGS: 00010202 RAX: 0000000000000000 RBX: 00007f9931868700 RCX: 00007f993206ac00 RDX: 0000000000000001 RSI: 0000000000000000 RDI: 00007ffc13e06ee0 RBP: 0000000000000100 R08: 0000000000000000 R09: 00007f9931868700 R10: 00007f99318689d0 R11: 0000000000000202 R12: 00007ffc13e06ee0 R13: 0000000000000c00 R14: 00007ffc13e06e00 R15: 00007f993206a000 Fixes: 726218fdc22c ("netfs: Define an interface to talk to a cache") Signed-off-by: David Howells <dhowells@redhat.com> Tested-by: Jeff Layton <jlayton@kernel.org> cc: Jan Kara <jack@suse.cz> cc: linux-cachefs@redhat.com cc: linux-fsdevel@vger.kernel.org Link: https://lore.kernel.org/r/20210922110420.GA21576@quack2.suse.cz/ [1] Link: https://lore.kernel.org/r/163887597541.1596626.2668163316598972956.stgit@warthog.procyon.org.uk/ # v1 Signed-off-by: Sasha Levin <sashal@kernel.org>
2021-10-05netfs: Fix READ/WRITE confusion when calling iov_iter_xarray()David Howells1-1/+1
Fix netfs_clear_unread() to pass READ to iov_iter_xarray() instead of WRITE (the flag is about the operation accessing the buffer, not what sort of access it is doing to the buffer). Fixes: 3d3c95046742 ("netfs: Provide readahead and readpage netfs helpers") Signed-off-by: David Howells <dhowells@redhat.com> Reviewed-by: Jeff Layton <jlayton@kernel.org> cc: linux-cachefs@redhat.com cc: linux-afs@lists.infradead.org cc: ceph-devel@vger.kernel.org cc: linux-cifs@vger.kernel.org cc: linux-nfs@vger.kernel.org cc: v9fs-developer@lists.sourceforge.net cc: linux-fsdevel@vger.kernel.org cc: linux-mm@kvack.org Link: https://lore.kernel.org/r/162729351325.813557.9242842205308443901.stgit@warthog.procyon.org.uk/ Link: https://lore.kernel.org/r/162886603464.3940407.3790841170414793899.stgit@warthog.procyon.org.uk Link: https://lore.kernel.org/r/163239074602.1243337.14154704004485867017.stgit@warthog.procyon.org.uk
2021-06-21netfs: fix test for whether we can skip read when writing beyond EOFJeff Layton1-13/+36
It's not sufficient to skip reading when the pos is beyond the EOF. There may be data at the head of the page that we need to fill in before the write. Add a new helper function that corrects and clarifies the logic of when we can skip reads, and have it only zero out the part of the page that won't have data copied in for the write. Finally, don't set the page Uptodate after zeroing. It's not up to date since the write data won't have been copied in yet. [DH made the following changes: - Prefixed the new function with "netfs_". - Don't call zero_user_segments() for a full-page write. - Altered the beyond-last-page check to avoid a DIV instruction and got rid of then-redundant zero-length file check. ] Fixes: e1b1240c1ff5f ("netfs: Add write_begin helper") Reported-by: Andrew W Elble <aweits@rit.edu> Signed-off-by: Jeff Layton <jlayton@kernel.org> Signed-off-by: David Howells <dhowells@redhat.com> Reviewed-by: Matthew Wilcox (Oracle) <willy@infradead.org> cc: ceph-devel@vger.kernel.org Link: https://lore.kernel.org/r/20210613233345.113565-1-jlayton@kernel.org/ Link: https://lore.kernel.org/r/162367683365.460125.4467036947364047314.stgit@warthog.procyon.org.uk/ # v1 Link: https://lore.kernel.org/r/162391826758.1173366.11794946719301590013.stgit@warthog.procyon.org.uk/ # v2
2021-05-25netfs: Make CONFIG_NETFS_SUPPORT auto-selected rather than manualDavid Howells1-1/+1
Make the netfs helper library selected automatically by the things that use it rather than being manually configured, even though it's required[1]. Fixes: 3a5829fefd3b ("netfs: Make a netfs helper module") Reported-by: Geert Uytterhoeven <geert@linux-m68k.org> Signed-off-by: David Howells <dhowells@redhat.com> Reviewed-by: Jeff Layton <jlayton@kernel.org> cc: linux-mm@kvack.org cc: linux-cachefs@redhat.com cc: linux-afs@lists.infradead.org cc: linux-nfs@vger.kernel.org cc: linux-cifs@vger.kernel.org cc: ceph-devel@vger.kernel.org cc: v9fs-developer@lists.sourceforge.net cc: linux-fsdevel@vger.kernel.org Link: https://lore.kernel.org/r/CAMuHMdXJZ7iNQE964CdBOU=vRKVMFzo=YF_eiwsGgqzuvZ+TuA@mail.gmail.com [1] Link: https://lore.kernel.org/r/162090298141.3166007.2971118149366779916.stgit@warthog.procyon.org.uk # v1
2021-05-25netfs: Pass flags through to grab_cache_page_write_begin()David Howells1-1/+1
In netfs_write_begin(), pass the AOP flags through to grab_cache_page_write_begin() so that a request to use GFP_NOFS is honoured. Fixes: e1b1240c1ff5 ("netfs: Add write_begin helper") Reported-by: Matthew Wilcox (Oracle) <willy@infradead.org> Signed-off-by: David Howells <dhowells@redhat.com> Reviewed-by: Jeff Layton <jlayton@kernel.org> Reviewed-by: Matthew Wilcox (Oracle) <willy@infradead.org> cc: linux-mm@kvack.org cc: linux-cachefs@redhat.com cc: linux-afs@lists.infradead.org cc: linux-nfs@vger.kernel.org cc: linux-cifs@vger.kernel.org cc: ceph-devel@vger.kernel.org cc: v9fs-developer@lists.sourceforge.net cc: linux-fsdevel@vger.kernel.org Link: https://lore.kernel.org/r/162090295383.3165945.13595101698295243662.stgit@warthog.procyon.org.uk # v1
2021-04-27netfs: Miscellaneous fixesDavid Howells1-3/+3
Fix some miscellaneous things in the new netfs lib[1]: (1) The kerneldoc for netfs_readpage() shouldn't say netfs_page(). (2) netfs_readpage() can get an integer overflow on 32-bit when it multiplies page_index(page) by PAGE_SIZE. It should use page_file_offset() instead. (3) netfs_write_begin() should use page_offset() to avoid the same overflow. Note that netfs_readpage() needs to use page_file_offset() rather than page_offset() as it may see swap-over-NFS. Reported-by: Matthew Wilcox (Oracle) <willy@infradead.org> Signed-off-by: David Howells <dhowells@redhat.com> Reviewed-by: Matthew Wilcox (Oracle) <willy@infradead.org> Reviewed-by: Jeff Layton <jlayton@kernel.org> Link: https://lore.kernel.org/r/161789062190.6155.12711584466338493050.stgit@warthog.procyon.org.uk/ [1]
2021-04-23netfs: Add a tracepoint to log failures that would be otherwise unseenDavid Howells1-2/+12
Add a tracepoint to log internal failures (such as cache errors) that we don't otherwise want to pass back to the netfs. Signed-off-by: David Howells <dhowells@redhat.com> Tested-by: Jeff Layton <jlayton@kernel.org> Tested-by: Dave Wysochanski <dwysocha@redhat.com> Tested-By: Marc Dionne <marc.dionne@auristor.com> cc: Matthew Wilcox <willy@infradead.org> cc: linux-mm@kvack.org cc: linux-cachefs@redhat.com cc: linux-afs@lists.infradead.org cc: linux-nfs@vger.kernel.org cc: linux-cifs@vger.kernel.org cc: ceph-devel@vger.kernel.org cc: v9fs-developer@lists.sourceforge.net cc: linux-fsdevel@vger.kernel.org Link: https://lore.kernel.org/r/161781048813.463527.1557000804674707986.stgit@warthog.procyon.org.uk/ Link: https://lore.kernel.org/r/161789082749.6155.15498680577213140870.stgit@warthog.procyon.org.uk/ # v6
2021-04-23netfs: Define an interface to talk to a cacheDavid Howells1-1/+238
Add an interface to the netfs helper library for reading data from the cache instead of downloading it from the server and support for writing data just downloaded or cleared to the cache. The API passes an iov_iter to the cache read/write routines to indicate the data/buffer to be used. This is done using the ITER_XARRAY type to provide direct access to the netfs inode's pagecache. When the netfs's ->begin_cache_operation() method is called, this must fill in the cache_resources in the netfs_read_request struct, including the netfs_cache_ops used by the helper lib to talk to the cache. The helper lib does not directly access the cache. Changes: v6: - Call trace_netfs_read() after beginning the cache op so that the cookie debug ID can be logged[3]. - Don't record the error from writing to the cache. We don't want to pass it back to the netfs[4]. - Fix copy-to-cache subreq amalgamation to not round up as it goes along otherwise it overcalculates the length of the write[5]. v5: - Use end_page_fscache() rather than unlock_page_fscache()[2]. v4: - Added flag to netfs_subreq_terminated() to indicate that the caller may have been running async and stuff that might sleep needs punting to a workqueue (can't use in_softirq()[1]). - Add missing inc of netfs_n_rh_read stat. - Move initial definition of fscache_begin_read_operation() elsewhere. - Need to call op->begin_cache_operation() from netfs_write_begin(). Signed-off-by: David Howells <dhowells@redhat.com> Reviewed-and-tested-by: Jeff Layton <jlayton@kernel.org> Tested-by: Dave Wysochanski <dwysocha@redhat.com> Tested-By: Marc Dionne <marc.dionne@auristor.com> cc: Matthew Wilcox <willy@infradead.org> cc: linux-mm@kvack.org cc: linux-cachefs@redhat.com cc: linux-afs@lists.infradead.org cc: linux-nfs@vger.kernel.org cc: linux-cifs@vger.kernel.org cc: ceph-devel@vger.kernel.org cc: v9fs-developer@lists.sourceforge.net cc: linux-fsdevel@vger.kernel.org Link: https://lore.kernel.org/r/20210216084230.GA23669@lst.de/ [1] Link: https://lore.kernel.org/r/2499407.1616505440@warthog.procyon.org.uk/ [2] Link: https://lore.kernel.org/r/161781045123.463527.14533348855710902201.stgit@warthog.procyon.org.uk/ [3] Link: https://lore.kernel.org/r/161781046256.463527.18158681600085556192.stgit@warthog.procyon.org.uk/ [4] Link: https://lore.kernel.org/r/161781047695.463527.7463536103593997492.stgit@warthog.procyon.org.uk/ [5] Link: https://lore.kernel.org/r/161118141321.1232039.8296910406755622458.stgit@warthog.procyon.org.uk/ # rfc Link: https://lore.kernel.org/r/161161036700.2537118.11170748455436854978.stgit@warthog.procyon.org.uk/ # v2 Link: https://lore.kernel.org/r/161340399569.1303470.1138884774643385730.stgit@warthog.procyon.org.uk/ # v3 Link: https://lore.kernel.org/r/161539542874.286939.13337898213448136687.stgit@warthog.procyon.org.uk/ # v4 Link: https://lore.kernel.org/r/161653799826.2770958.9015430297426331950.stgit@warthog.procyon.org.uk/ # v5 Link: https://lore.kernel.org/r/161789081462.6155.3853904866933313256.stgit@warthog.procyon.org.uk/ # v6
2021-04-23netfs: Add write_begin helperDavid Howells3-3/+174
Add a helper to do the pre-reading work for the netfs write_begin address space op. Changes v6: - Fixed a missing rreq put in netfs_write_begin()[3]. - Use DEFINE_READAHEAD()[4]. v5: - Made the wait for PG_fscache in netfs_write_begin() killable[2]. v4: - Added flag to netfs_subreq_terminated() to indicate that the caller may have been running async and stuff that might sleep needs punting to a workqueue (can't use in_softirq()[1]). Signed-off-by: David Howells <dhowells@redhat.com> Reviewed-and-tested-by: Jeff Layton <jlayton@kernel.org> Tested-by: Dave Wysochanski <dwysocha@redhat.com> Tested-By: Marc Dionne <marc.dionne@auristor.com> cc: Matthew Wilcox <willy@infradead.org> cc: linux-mm@kvack.org cc: linux-cachefs@redhat.com cc: linux-afs@lists.infradead.org cc: linux-nfs@vger.kernel.org cc: linux-cifs@vger.kernel.org cc: ceph-devel@vger.kernel.org cc: v9fs-developer@lists.sourceforge.net cc: linux-fsdevel@vger.kernel.org Link: https://lore.kernel.org/r/20210216084230.GA23669@lst.de/ [1] Link: https://lore.kernel.org/r/2499407.1616505440@warthog.procyon.org.uk/ [2] Link: https://lore.kernel.org/r/161781042127.463527.9154479794406046987.stgit@warthog.procyon.org.uk/ [3] Link: https://lore.kernel.org/r/1234933.1617886271@warthog.procyon.org.uk/ [4] Link: https://lore.kernel.org/r/160588543960.3465195.2792938973035886168.stgit@warthog.procyon.org.uk/ # rfc Link: https://lore.kernel.org/r/161118140165.1232039.16418853874312234477.stgit@warthog.procyon.org.uk/ # rfc Link: https://lore.kernel.org/r/161161035539.2537118.15674887534950908530.stgit@warthog.procyon.org.uk/ # v2 Link: https://lore.kernel.org/r/161340398368.1303470.11242918276563276090.stgit@warthog.procyon.org.uk/ # v3 Link: https://lore.kernel.org/r/161539541541.286939.1889738674057013729.stgit@warthog.procyon.org.uk/ # v4 Link: https://lore.kernel.org/r/161653798616.2770958.17213315845968485563.stgit@warthog.procyon.org.uk/ # v5 Link: https://lore.kernel.org/r/161789080530.6155.1011847312392330491.stgit@warthog.procyon.org.uk/ # v6
2021-04-23netfs: Gather statsDavid Howells5-2/+127
Gather statistics from the netfs interface that can be exported through a seqfile. This is intended to be called by a later patch when viewing /proc/fs/fscache/stats. Signed-off-by: David Howells <dhowells@redhat.com> Reviewed-and-tested-by: Jeff Layton <jlayton@kernel.org> Tested-by: Dave Wysochanski <dwysocha@redhat.com> Tested-By: Marc Dionne <marc.dionne@auristor.com> cc: Matthew Wilcox <willy@infradead.org> cc: linux-mm@kvack.org cc: linux-cachefs@redhat.com cc: linux-afs@lists.infradead.org cc: linux-nfs@vger.kernel.org cc: linux-cifs@vger.kernel.org cc: ceph-devel@vger.kernel.org cc: v9fs-developer@lists.sourceforge.net cc: linux-fsdevel@vger.kernel.org Link: https://lore.kernel.org/r/161118139247.1232039.10556850937548511068.stgit@warthog.procyon.org.uk/ # rfc Link: https://lore.kernel.org/r/161161034669.2537118.2761232524997091480.stgit@warthog.procyon.org.uk/ # v2 Link: https://lore.kernel.org/r/161340397101.1303470.17581910581108378458.stgit@warthog.procyon.org.uk/ # v3 Link: https://lore.kernel.org/r/161539539959.286939.6794352576462965914.stgit@warthog.procyon.org.uk/ # v4 Link: https://lore.kernel.org/r/161653797700.2770958.5801990354413178228.stgit@warthog.procyon.org.uk/ # v5 Link: https://lore.kernel.org/r/161789079281.6155.17141344853277186500.stgit@warthog.procyon.org.uk/ # v6
2021-04-23netfs: Add tracepointsDavid Howells1-0/+26
Add three tracepoints to track the activity of the read helpers: (1) netfs/netfs_read This logs entry to the read helpers and also expansion of the range in a readahead request. (2) netfs/netfs_rreq This logs the progress of netfs_read_request objects which track read requests. A read request may be a compound of multiple subrequests. (3) netfs/netfs_sreq This logs the progress of netfs_read_subrequest objects, which track the contributions from various sources to a read request. Signed-off-by: David Howells <dhowells@redhat.com> Reviewed-and-tested-by: Jeff Layton <jlayton@kernel.org> Tested-by: Dave Wysochanski <dwysocha@redhat.com> Tested-By: Marc Dionne <marc.dionne@auristor.com> cc: Matthew Wilcox <willy@infradead.org> cc: linux-mm@kvack.org cc: linux-cachefs@redhat.com cc: linux-afs@lists.infradead.org cc: linux-nfs@vger.kernel.org cc: linux-cifs@vger.kernel.org cc: ceph-devel@vger.kernel.org cc: v9fs-developer@lists.sourceforge.net cc: linux-fsdevel@vger.kernel.org Link: https://lore.kernel.org/r/161118138060.1232039.5353374588021776217.stgit@warthog.procyon.org.uk/ # rfc Link: https://lore.kernel.org/r/161161033468.2537118.14021843889844001905.stgit@warthog.procyon.org.uk/ # v2 Link: https://lore.kernel.org/r/161340395843.1303470.7355519662919639648.stgit@warthog.procyon.org.uk/ # v3 Link: https://lore.kernel.org/r/161539538693.286939.10171713520419106334.stgit@warthog.procyon.org.uk/ # v4 Link: https://lore.kernel.org/r/161653796447.2770958.1870655382450862155.stgit@warthog.procyon.org.uk/ # v5 Link: https://lore.kernel.org/r/161789078003.6155.17814844411672989942.stgit@warthog.procyon.org.uk/ # v6
2021-04-23netfs: Provide readahead and readpage netfs helpersDavid Howells3-0/+792
Add a pair of helper functions: (*) netfs_readahead() (*) netfs_readpage() to do the work of handling a readahead or a readpage, where the page(s) that form part of the request may be split between the local cache, the server or just require clearing, and may be single pages and transparent huge pages. This is all handled within the helper. Note that while both will read from the cache if there is data present, only netfs_readahead() will expand the request beyond what it was asked to do, and only netfs_readahead() will write back to the cache. netfs_readpage(), on the other hand, is synchronous and only fetches the page (which might be a THP) it is asked for. The netfs gives the helper parameters from the VM, the cache cookie it wants to use (or NULL) and a table of operations (only one of which is mandatory): (*) expand_readahead() [optional] Called to allow the netfs to request an expansion of a readahead request to meet its own alignment requirements. This is done by changing rreq->start and rreq->len. (*) clamp_length() [optional] Called to allow the netfs to cut down a subrequest to meet its own boundary requirements. If it does this, the helper will generate additional subrequests until the full request is satisfied. (*) is_still_valid() [optional] Called to find out if the data just read from the cache has been invalidated and must be reread from the server. (*) issue_op() [required] Called to ask the netfs to issue a read to the server. The subrequest describes the read. The read request holds information about the file being accessed. The netfs can cache information in rreq->netfs_priv. Upon completion, the netfs should set the error, transferred and can also set FSCACHE_SREQ_CLEAR_TAIL and then call fscache_subreq_terminated(). (*) done() [optional] Called after the pages have been unlocked. The read request is still pinning the file and mapping and may still be pinning pages with PG_fscache. rreq->error indicates any error that has been accumulated. (*) cleanup() [optional] Called when the helper is disposing of a finished read request. This allows the netfs to clear rreq->netfs_priv. Netfs support is enabled with CONFIG_NETFS_SUPPORT=y. It will be built even if CONFIG_FSCACHE=n and in this case much of it should be optimised away, allowing the filesystem to use it even when caching is disabled. Changes: v5: - Comment why netfs_readahead() is putting pages[2]. - Use page_file_mapping() rather than page->mapping[2]. - Use page_index() rather than page->index[2]. - Use set_page_fscache()[3] rather then SetPageFsCache() as this takes an appropriate ref too[4]. v4: - Folded in a kerneldoc comment fix. - Folded in a fix for the error handling in the case that ENOMEM occurs. - Added flag to netfs_subreq_terminated() to indicate that the caller may have been running async and stuff that might sleep needs punting to a workqueue (can't use in_softirq()[1]). Signed-off-by: David Howells <dhowells@redhat.com> Reviewed-and-tested-by: Jeff Layton <jlayton@kernel.org> Tested-by: Dave Wysochanski <dwysocha@redhat.com> Tested-By: Marc Dionne <marc.dionne@auristor.com> cc: Matthew Wilcox <willy@infradead.org> cc: linux-mm@kvack.org cc: linux-cachefs@redhat.com cc: linux-afs@lists.infradead.org cc: linux-nfs@vger.kernel.org cc: linux-cifs@vger.kernel.org cc: ceph-devel@vger.kernel.org cc: v9fs-developer@lists.sourceforge.net cc: linux-fsdevel@vger.kernel.org Link: https://lore.kernel.org/r/20210216084230.GA23669@lst.de/ [1] Link: https://lore.kernel.org/r/20210321014202.GF3420@casper.infradead.org/ [2] Link: https://lore.kernel.org/r/2499407.1616505440@warthog.procyon.org.uk/ [3] Link: https://lore.kernel.org/r/CAHk-=wh+2gbF7XEjYc=HV9w_2uVzVf7vs60BPz0gFA=+pUm3ww@mail.gmail.com/ [4] Link: https://lore.kernel.org/r/160588497406.3465195.18003475695899726222.stgit@warthog.procyon.org.uk/ # rfc Link: https://lore.kernel.org/r/161118136849.1232039.8923686136144228724.stgit@warthog.procyon.org.uk/ # rfc Link: https://lore.kernel.org/r/161161032290.2537118.13400578415247339173.stgit@warthog.procyon.org.uk/ # v2 Link: https://lore.kernel.org/r/161340394873.1303470.6237319335883242536.stgit@warthog.procyon.org.uk/ # v3 Link: https://lore.kernel.org/r/161539537375.286939.16642940088716990995.stgit@warthog.procyon.org.uk/ # v4 Link: https://lore.kernel.org/r/161653795430.2770958.4947584573720000554.stgit@warthog.procyon.org.uk/ # v5 Link: https://lore.kernel.org/r/161789076581.6155.6745849361504760209.stgit@warthog.procyon.org.uk/ # v6
2021-04-23netfs: Make a netfs helper moduleDavid Howells1-0/+8
Make a netfs helper module to manage read request segmentation, caching support and transparent huge page support on behalf of a network filesystem. Signed-off-by: David Howells <dhowells@redhat.com> Reviewed-and-tested-by: Jeff Layton <jlayton@redhat.com> Tested-by: Dave Wysochanski <dwysocha@redhat.com> Tested-By: Marc Dionne <marc.dionne@auristor.com> cc: Matthew Wilcox <willy@infradead.org> cc: linux-mm@kvack.org cc: linux-cachefs@redhat.com cc: linux-afs@lists.infradead.org cc: linux-nfs@vger.kernel.org cc: linux-cifs@vger.kernel.org cc: ceph-devel@vger.kernel.org cc: v9fs-developer@lists.sourceforge.net cc: linux-fsdevel@vger.kernel.org Link: https://lore.kernel.org/r/160588496284.3465195.10102643717770106661.stgit@warthog.procyon.org.uk/ # rfc Link: https://lore.kernel.org/r/161118135638.1232039.1622182202673126285.stgit@warthog.procyon.org.uk/ # rfc Link: https://lore.kernel.org/r/161161031028.2537118.1213974428943508753.stgit@warthog.procyon.org.uk/ # v2 Link: https://lore.kernel.org/r/161340391427.1303470.14884950716721956560.stgit@warthog.procyon.org.uk/ # v3 Link: https://lore.kernel.org/r/161539531569.286939.18317119181653706665.stgit@warthog.procyon.org.uk/ # v4 Link: https://lore.kernel.org/r/161653790328.2770958.6710423217716151549.stgit@warthog.procyon.org.uk/ # v5 Link: https://lore.kernel.org/r/161789071202.6155.16519256513958534906.stgit@warthog.procyon.org.uk/ # v6
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