kernel/linux.git/include/trace/events/netfs.h, branch v6.12.91

netfs: In readahead, put the folio refs as soon extracted

2024-10-07T11:48:22+00:00

netfslib currently defers dropping the ref on the folios it obtains during readahead to after it has started I/O on the basis that we can do it whilst we wait for the I/O to complete, but this runs the risk of the I/O collection racing with this in future. Furthermore, Matthew Wilcox strongly suggests that the refs should be dropped immediately, as readahead_folio() does (netfslib is using __readahead_batch() which doesn't drop the refs). Fixes: ee4cdf7ba857 ("netfs: Speed up buffered reading") Suggested-by: Matthew Wilcox Signed-off-by: David Howells Link: https://lore.kernel.org/r/3771538.1728052438@warthog.procyon.org.uk cc: Jeff Layton cc: netfs@lists.linux.dev cc: linux-fsdevel@vger.kernel.org Signed-off-by: Christian Brauner

netfs: Fix the netfs_folio tracepoint to handle NULL mapping

2024-09-30T12:11:05+00:00

Fix the netfs_folio tracepoint to handle folios that have a NULL mapping pointer. In such a case, just substitute a zero inode number. Fixes: c38f4e96e605 ("netfs: Provide func to copy data to pagecache for buffered write") Signed-off-by: David Howells Link: https://lore.kernel.org/r/2917423.1727697556@warthog.procyon.org.uk cc: Jeff Layton cc: netfs@lists.linux.dev cc: linux-fsdevel@vger.kernel.org Signed-off-by: Christian Brauner

netfs: Cancel dirty folios that have no storage destination

2024-09-12T10:20:41+00:00

Kafs wants to be able to cache the contents of directories (and symlinks), but whilst these are downloaded from the server with the FS.FetchData RPC op and similar, the same as for regular files, they can't be updated by FS.StoreData, but rather have special operations (FS.MakeDir, etc.). Now, rather than redownloading a directory's content after each change made to that directory, kafs modifies the local blob. This blob can be saved out to the cache, and since it's using netfslib, kafs just marks the folios dirty and lets ->writepages() on the directory take care of it, as for an regular file. This is fine as long as there's a cache as although the upload stream is disabled, there's a cache stream to drive the procedure. But if the cache goes away in the meantime, suddenly there's no way do any writes and the code gets confused, complains "R=%x: No submit" to dmesg and leaves the dirty folio hanging. Fix this by just cancelling the store of the folio if neither stream is active. (If there's no cache at the time of dirtying, we should just not mark the folio dirty). Signed-off-by: David Howells cc: Jeff Layton cc: netfs@lists.linux.dev cc: linux-fsdevel@vger.kernel.org Link: https://lore.kernel.org/r/20240814203850.2240469-23-dhowells@redhat.com/ # v2 Signed-off-by: Christian Brauner

netfs: Speed up buffered reading

2024-09-12T10:20:41+00:00

Improve the efficiency of buffered reads in a number of ways: (1) Overhaul the algorithm in general so that it's a lot more compact and split the read submission code between buffered and unbuffered versions. The unbuffered version can be vastly simplified. (2) Read-result collection is handed off to a work queue rather than being done in the I/O thread. Multiple subrequests can be processes simultaneously. (3) When a subrequest is collected, any folios it fully spans are collected and "spare" data on either side is donated to either the previous or the next subrequest in the sequence. Notes: (*) Readahead expansion is massively slows down fio, presumably because it causes a load of extra allocations, both folio and xarray, up front before RPC requests can be transmitted. (*) RDMA with cifs does appear to work, both with SIW and RXE. (*) PG_private_2-based reading and copy-to-cache is split out into its own file and altered to use folio_queue. Note that the copy to the cache now creates a new write transaction against the cache and adds the folios to be copied into it. This allows it to use part of the writeback I/O code. Signed-off-by: David Howells cc: Jeff Layton cc: netfs@lists.linux.dev cc: linux-fsdevel@vger.kernel.org Link: https://lore.kernel.org/r/20240814203850.2240469-20-dhowells@redhat.com/ # v2 Signed-off-by: Christian Brauner

netfs: Simplify the writeback code

2024-09-12T10:20:40+00:00

Use the new folio_queue structures to simplify the writeback code. The problem with referring to the i_pages xarray directly is that we may have gaps in the sequence of folios we're writing from that we need to skip when we're removing the writeback mark from the folios we're writing back from. At the moment the code tries to deal with this by carefully tracking the gaps in each writeback stream (eg. write to server and write to cache) and divining when there's a gap that spans folios (something that's not helped by folios not being a consistent size). Instead, the folio_queue buffer contains pointers only the folios we're dealing with, has them in ascending order and indicates a gap by placing non-consequitive folios next to each other. This makes it possible to track where we need to clean up to by just keeping track of where we've processed to on each stream and taking the minimum. Note that the I/O iterator is always rounded up to the end of the folio, even if that is beyond the EOF position, so that the cache can do DIO from the page. The excess space is cleared, though mmapped writes clobber it. Signed-off-by: David Howells cc: Jeff Layton cc: netfs@lists.linux.dev cc: linux-fsdevel@vger.kernel.org Link: https://lore.kernel.org/r/20240814203850.2240469-18-dhowells@redhat.com/ # v2 Signed-off-by: Christian Brauner

netfs: Use new folio_queue data type and iterator instead of xarray iter

2024-09-12T10:20:40+00:00

Make the netfs write-side routines use the new folio_queue struct to hold a rolling buffer of folios, with the issuer adding folios at the tail and the collector removing them from the head as they're processed instead of using an xarray. This will allow a subsequent patch to simplify the write collector. The primary mark (as tested by folioq_is_marked()) is used to note if the corresponding folio needs putting. Signed-off-by: David Howells cc: Jeff Layton cc: netfs@lists.linux.dev cc: linux-fsdevel@vger.kernel.org Link: https://lore.kernel.org/r/20240814203850.2240469-16-dhowells@redhat.com/ # v2 Signed-off-by: Christian Brauner

netfs: Remove NETFS_COPY_TO_CACHE

2024-09-05T09:00:42+00:00

Remove NETFS_COPY_TO_CACHE as it isn't used anymore. Signed-off-by: David Howells cc: Jeff Layton cc: netfs@lists.linux.dev cc: linux-fsdevel@vger.kernel.org Link: https://lore.kernel.org/r/20240814203850.2240469-10-dhowells@redhat.com/ # v2 Signed-off-by: Christian Brauner

netfs: Reserve netfs_sreq_source 0 as unset/unknown

2024-09-05T09:00:41+00:00

Reserve the 0-valued netfs_sreq_source to mean unset or unknown so that it can be seen in the trace as such rather than appearing as download-from-server when it's going to get switched to something else. Signed-off-by: David Howells cc: Jeff Layton cc: netfs@lists.linux.dev cc: linux-fsdevel@vger.kernel.org Link: https://lore.kernel.org/r/20240814203850.2240469-9-dhowells@redhat.com/ # v2 Signed-off-by: Christian Brauner

netfs: Reduce number of conditional branches in netfs_perform_write()

2024-09-05T09:00:41+00:00

Reduce the number of conditional branches in netfs_perform_write() by merging in netfs_how_to_modify() and then creating a separate if-statement for each way we might modify a folio. Note that this means replicating the data copy in each path. Signed-off-by: David Howells cc: Jeff Layton cc: netfs@lists.linux.dev cc: linux-fsdevel@vger.kernel.org Link: https://lore.kernel.org/r/20240814203850.2240469-6-dhowells@redhat.com/ # v2 Signed-off-by: Christian Brauner

netfs: Fix handling of USE_PGPRIV2 and WRITE_TO_CACHE flags

2024-08-12T20:03:27+00:00

The NETFS_RREQ_USE_PGPRIV2 and NETFS_RREQ_WRITE_TO_CACHE flags aren't used correctly. The problem is that we try to set them up in the request initialisation, but we the cache may be in the process of setting up still, and so the state may not be correct. Further, we secondarily sample the cache state and make contradictory decisions later. The issue arises because we set up the cache resources, which allows the cache's ->prepare_read() to switch on NETFS_SREQ_COPY_TO_CACHE - which triggers cache writing even if we didn't set the flags when allocating. Fix this in the following way: (1) Drop NETFS_ICTX_USE_PGPRIV2 and instead set NETFS_RREQ_USE_PGPRIV2 in ->init_request() rather than trying to juggle that in netfs_alloc_request(). (2) Repurpose NETFS_RREQ_USE_PGPRIV2 to merely indicate that if caching is to be done, then PG_private_2 is to be used rather than only setting it if we decide to cache and then having netfs_rreq_unlock_folios() set the non-PG_private_2 writeback-to-cache if it wasn't set. (3) Split netfs_rreq_unlock_folios() into two functions, one of which contains the deprecated code for using PG_private_2 to avoid accidentally doing the writeback path - and always use it if USE_PGPRIV2 is set. (4) As NETFS_ICTX_USE_PGPRIV2 is removed, make netfs_write_begin() always wait for PG_private_2. This function is deprecated and only used by ceph anyway, and so label it so. (5) Drop the NETFS_RREQ_WRITE_TO_CACHE flag and use fscache_operation_valid() on the cache_resources instead. This has the advantage of picking up the result of netfs_begin_cache_read() and fscache_begin_write_operation() - which are called after the object is initialised and will wait for the cache to come to a usable state. Just reverting ae678317b95e[1] isn't a sufficient fix, so this need to be applied on top of that. Without this as well, things like: rcu: INFO: rcu_sched detected expedited stalls on CPUs/tasks: { and: WARNING: CPU: 13 PID: 3621 at fs/ceph/caps.c:3386 may happen, along with some UAFs due to PG_private_2 not getting used to wait on writeback completion. Fixes: 2ff1e97587f4 ("netfs: Replace PG_fscache by setting folio->private and marking dirty") Reported-by: Max Kellermann Signed-off-by: David Howells cc: Ilya Dryomov cc: Xiubo Li cc: Hristo Venev cc: Jeff Layton cc: Matthew Wilcox cc: ceph-devel@vger.kernel.org cc: netfs@lists.linux.dev cc: linux-fsdevel@vger.kernel.org cc: linux-mm@kvack.org Link: https://lore.kernel.org/r/3575457.1722355300@warthog.procyon.org.uk/ [1] Link: https://lore.kernel.org/r/1173209.1723152682@warthog.procyon.org.uk Signed-off-by: Christian Brauner