kernel/git/stable/linux.git/Documentation/filesystems/caching/netfs-api.txt, branch master

docs: filesystems: caching/netfs-api.txt: convert it to ReST

2020-05-05T15:22:20+00:00

- Add a SPDX header; - Adjust document and section titles; - Some whitespace fixes and new line breaks; - Mark literal blocks as such; - Add it to filesystems/caching/index.rst. Signed-off-by: Mauro Carvalho Chehab Link: https://lore.kernel.org/r/cfe4cb1bf8e1f0093d44c30801ec42e74721e543.1588021877.git.mchehab+huawei@kernel.org Signed-off-by: Jonathan Corbet

Documentation: Use "while" instead of "whilst"

2018-11-20T16:30:43+00:00

Whilst making an unrelated change to some Documentation, Linus sayeth: | Afaik, even in Britain, "whilst" is unusual and considered more | formal, and "while" is the common word. | | [...] | | Can we just admit that we work with computers, and we don't need to | use þe eald Englisc spelling of words that most of the world never | uses? dictionary.com refers to the word as "Chiefly British", which is probably an undesirable attribute for technical documentation. Replace all occurrences under Documentation/ with "while". Cc: David Howells Cc: Liam Girdwood Cc: Chris Wilson Cc: Michael Halcrow Cc: Jonathan Corbet Reported-by: Linus Torvalds Signed-off-by: Will Deacon Signed-off-by: Jonathan Corbet

fscache: Pass object size in rather than calling back for it

2018-04-06T13:05:14+00:00

Pass the object size in to fscache_acquire_cookie() and fscache_write_page() rather than the netfs providing a callback by which it can be received. This makes it easier to update the size of the object when a new page is written that extends the object. The current object size is also passed by fscache to the check_aux function, obviating the need to store it in the aux data. Signed-off-by: David Howells Acked-by: Anna Schumaker Tested-by: Steve Dickson

fscache: Attach the index key and aux data to the cookie

2018-04-04T12:41:28+00:00

Attach copies of the index key and auxiliary data to the fscache cookie so that: (1) The callbacks to the netfs for this stuff can be eliminated. This can simplify things in the cache as the information is still available, even after the cache has relinquished the cookie. (2) Simplifies the locking requirements of accessing the information as we don't have to worry about the netfs object going away on us. (3) The cache can do lazy updating of the coherency information on disk. As long as the cache is flushed before reboot/poweroff, there's no need to update the coherency info on disk every time it changes. (4) Cookies can be hashed or put in a tree as the index key is easily available. This allows: (a) Checks for duplicate cookies can be made at the top fscache layer rather than down in the bowels of the cache backend. (b) Caching can be added to a netfs object that has a cookie if the cache is brought online after the netfs object is allocated. A certain amount of space is made in the cookie for inline copies of the data, but if it won't fit there, extra memory will be allocated for it. The downside of this is that live cache operation requires more memory. Signed-off-by: David Howells Acked-by: Anna Schumaker Tested-by: Steve Dickson

fscache: remove unused ->now_uncached callback

2017-09-07T00:27:26+00:00

Patch series "Ranged pagevec lookup", v2. In this series I make pagevec_lookup() update the index (to be consistent with pagevec_lookup_tag() and also as a preparation for ranged lookups), provide ranged variant of pagevec_lookup() and use it in places where it makes sense. This not only removes some common code but is also a measurable performance win for some use cases (see patch 4/10) where radix tree is sparse and searching & grabing of a page after the end of the range has measurable overhead. This patch (of 10): The callback doesn't ever get called. Remove it. Link: http://lkml.kernel.org/r/20170726114704.7626-2-jack@suse.cz Signed-off-by: Jan Kara Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

FS-Cache: Provide the ability to enable/disable cookies

2013-09-27T17:40:25+00:00

Provide the ability to enable and disable fscache cookies. A disabled cookie will reject or ignore further requests to: Acquire a child cookie Invalidate and update backing objects Check the consistency of a backing object Allocate storage for backing page Read backing pages Write to backing pages but still allows: Checks/waits on the completion of already in-progress objects Uncaching of pages Relinquishment of cookies Two new operations are provided: (1) Disable a cookie: void fscache_disable_cookie(struct fscache_cookie *cookie, bool invalidate); If the cookie is not already disabled, this locks the cookie against other dis/enablement ops, marks the cookie as being disabled, discards or invalidates any backing objects and waits for cessation of activity on any associated object. This is a wrapper around a chunk split out of fscache_relinquish_cookie(), but it reinitialises the cookie such that it can be reenabled. All possible failures are handled internally. The caller should consider calling fscache_uncache_all_inode_pages() afterwards to make sure all page markings are cleared up. (2) Enable a cookie: void fscache_enable_cookie(struct fscache_cookie *cookie, bool (*can_enable)(void *data), void *data) If the cookie is not already enabled, this locks the cookie against other dis/enablement ops, invokes can_enable() and, if the cookie is not an index cookie, will begin the procedure of acquiring backing objects. The optional can_enable() function is passed the data argument and returns a ruling as to whether or not enablement should actually be permitted to begin. All possible failures are handled internally. The cookie will only be marked as enabled if provisional backing objects are allocated. A later patch will introduce these to NFS. Cookie enablement during nfs_open() is then contingent on i_writecount <= 0. can_enable() checks for a race between open(O_RDONLY) and open(O_WRONLY/O_RDWR). This simplifies NFS's cookie handling and allows us to get rid of open(O_RDONLY) accidentally introducing caching to an inode that's open for writing already. One operation has its API modified: (3) Acquire a cookie. struct fscache_cookie *fscache_acquire_cookie( struct fscache_cookie *parent, const struct fscache_cookie_def *def, void *netfs_data, bool enable); This now has an additional argument that indicates whether the requested cookie should be enabled by default. It doesn't need the can_enable() function because the caller must prevent multiple calls for the same netfs object and it doesn't need to take the enablement lock because no one else can get at the cookie before this returns. Signed-off-by: David Howells

fscache: Netfs function for cleanup post readpages

2013-09-06T08:17:30+00:00

Currently the fscache code expect the netfs to call fscache_readpages_or_alloc inside the aops readpages callback. It marks all the pages in the list provided by readahead with PG_private_2. In the cases that the netfs fails to read all the pages (which is legal) it ends up returning to the readahead and triggering a BUG. This happens because the page list still contains marked pages. This patch implements a simple fscache_readpages_cancel function that the netfs should call before returning from readpages. It will revoke the pages from the underlying cache backend and unmark them. The problem was originally worked out in the Ceph devel tree, but it also occurs in CIFS. It appears that NFS, AFS and 9P are okay as read_cache_pages() will clean up the unprocessed pages in the case of an error. This can be used to address the following oops: [12410647.597278] BUG: Bad page state in process petabucket pfn:3d504e [12410647.597292] page:ffffea000f541380 count:0 mapcount:0 mapping: (null) index:0x0 [12410647.597298] page flags: 0x200000000001000(private_2) ... [12410647.597334] Call Trace: [12410647.597345] [] dump_stack+0x19/0x1b [12410647.597356] [] bad_page+0xc7/0x120 [12410647.597359] [] free_pages_prepare+0x10e/0x120 [12410647.597361] [] free_hot_cold_page+0x40/0x170 [12410647.597363] [] __put_single_page+0x27/0x30 [12410647.597365] [] put_page+0x25/0x40 [12410647.597376] [] ceph_readpages+0x2e9/0x6e0 [ceph] [12410647.597379] [] __do_page_cache_readahead+0x1af/0x260 [12410647.597382] [] ra_submit+0x21/0x30 [12410647.597384] [] filemap_fault+0x254/0x490 [12410647.597387] [] __do_fault+0x6f/0x4e0 [12410647.597391] [] ? __switch_to+0x16d/0x4a0 [12410647.597395] [] ? finish_task_switch+0x5a/0xc0 [12410647.597398] [] handle_pte_fault+0xf6/0x930 [12410647.597401] [] ? pte_mfn_to_pfn+0x93/0x110 [12410647.597403] [] ? xen_pmd_val+0xe/0x10 [12410647.597405] [] ? __raw_callee_save_xen_pmd_val+0x11/0x1e [12410647.597407] [] handle_mm_fault+0x251/0x370 [12410647.597411] [] ? call_rwsem_down_read_failed+0x14/0x30 [12410647.597414] [] __do_page_fault+0x1aa/0x550 [12410647.597418] [] ? up_write+0x1d/0x20 [12410647.597422] [] ? vm_mmap_pgoff+0xbc/0xe0 [12410647.597425] [] ? SyS_mmap_pgoff+0xd8/0x240 [12410647.597427] [] do_page_fault+0xe/0x10 [12410647.597431] [] page_fault+0x28/0x30 Signed-off-by: Milosz Tanski Signed-off-by: David Howells

FS-Cache: Fix heading in documentation

2013-09-06T08:17:30+00:00

Fix a heading in the documentation to make it consistent with the contents list. Signed-off-by: David Howells

FS-Cache: Add interface to check consistency of a cached object

2013-09-06T08:17:30+00:00

Extend the fscache netfs API so that the netfs can ask as to whether a cache object is up to date with respect to its corresponding netfs object: int fscache_check_consistency(struct fscache_cookie *cookie) This will call back to the netfs to check whether the auxiliary data associated with a cookie is correct. It returns 0 if it is and -ESTALE if it isn't; it may also return -ENOMEM and -ERESTARTSYS. The backends now have to implement a mandatory operation pointer: int (*check_consistency)(struct fscache_object *object) that corresponds to the above API call. FS-Cache takes care of pinning the object and the cookie in memory and managing this call with respect to the object state. Original-author: Hongyi Jia Signed-off-by: David Howells cc: Hongyi Jia cc: Milosz Tanski

FS-Cache: Provide proper invalidation

2012-12-20T22:04:07+00:00

Provide a proper invalidation method rather than relying on the netfs retiring the cookie it has and getting a new one. The problem with this is that isn't easy for the netfs to make sure that it has completed/cancelled all its outstanding storage and retrieval operations on the cookie it is retiring. Instead, have the cache provide an invalidation method that will cancel or wait for all currently outstanding operations before invalidating the cache, and will cause new operations to queue up behind that. Whilst invalidation is in progress, some requests will be rejected until the cache can stack a barrier on the operation queue to cause new operations to be deferred behind it. Signed-off-by: David Howells