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Wed, 13 Dec 2023 15:25:30 +0000 (UTC) From: David Howells To: Jeff Layton , Steve French Cc: David Howells , Matthew Wilcox , Marc Dionne , Paulo Alcantara , Shyam Prasad N , Tom Talpey , Dominique Martinet , Eric Van Hensbergen , Ilya Dryomov , Christian Brauner , linux-cachefs@redhat.com, linux-afs@lists.infradead.org, linux-cifs@vger.kernel.org, linux-nfs@vger.kernel.org, ceph-devel@vger.kernel.org, v9fs@lists.linux.dev, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH v4 23/39] netfs: Prep to use folio->private for write grouping and streaming write Date: Wed, 13 Dec 2023 15:23:33 +0000 Message-ID: <20231213152350.431591-24-dhowells@redhat.com> In-Reply-To: <20231213152350.431591-1-dhowells@redhat.com> References: <20231213152350.431591-1-dhowells@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.4.1 on 10.11.54.10 X-Rspamd-Queue-Id: 199D11A001E X-Rspam-User: X-Rspamd-Server: rspam02 X-Stat-Signature: xnww8pny6a6qhnnkr548xf6gx9rgt753 X-HE-Tag: 1702481139-923670 X-HE-Meta: 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 7ZN6ON40 965a7j1UXnFnIrmtgoWQlRNS7qGWzcTfOCQ5aU7C23D3Q2ewcF7m583uMtpTWCQjBQHPqPuFbSFdJWpFJLCtK/qcBNXKjQdBOKYfhWFFMtpAtRr1el5k4+EhLR1x16XSSJIXlSUXRPEmokIVNyz4ocq1e+h07GhYhj0XlPBmXKowpte2VnA41DRjmFsHhi54CkLgk7RxldGs33mzhWTZicp4WMYzKpVSUiBiU/VGI/I/wtaxh/X1+ac0VY8iVPWrUCFjsrtFtxUCmchH+VPPld9hXeRUpDB5ZWLlH9Wag4xmlxCY= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: Prepare to use folio->private to hold information write grouping and streaming write. These are implemented in the same commit as they both make use of folio->private and will be both checked at the same time in several places. "Write grouping" involves ordering the writeback of groups of writes, such as is needed for ceph snaps. A group is represented by a filesystem-supplied object which must contain a netfs_group struct. This contains just a refcount and a pointer to a destructor. "Streaming write" is the storage of data in folios that are marked dirty, but not uptodate, to avoid unnecessary reads of data. This is represented by a netfs_folio struct. This contains the offset and length of the modified region plus the otherwise displaced write grouping pointer. The way folio->private is multiplexed is: (1) If private is NULL then neither is in operation on a dirty folio. (2) If private is set, with bit 0 clear, then this points to a group. (3) If private is set, with bit 0 set, then this points to a netfs_folio struct (with bit 0 AND'ed out). Signed-off-by: David Howells cc: Jeff Layton cc: linux-cachefs@redhat.com cc: linux-fsdevel@vger.kernel.org cc: linux-mm@kvack.org --- fs/netfs/internal.h | 28 ++++++++++++++++++++++++++ fs/netfs/misc.c | 46 +++++++++++++++++++++++++++++++++++++++++++ include/linux/netfs.h | 41 ++++++++++++++++++++++++++++++++++++++ 3 files changed, 115 insertions(+) diff --git a/fs/netfs/internal.h b/fs/netfs/internal.h index 8d1bfc9c3e2f..1b83c534593a 100644 --- a/fs/netfs/internal.h +++ b/fs/netfs/internal.h @@ -149,6 +149,34 @@ static inline bool netfs_is_cache_enabled(struct netfs_inode *ctx) #endif } +/* + * Get a ref on a netfs group attached to a dirty page (e.g. a ceph snap). + */ +static inline struct netfs_group *netfs_get_group(struct netfs_group *netfs_group) +{ + if (netfs_group) + refcount_inc(&netfs_group->ref); + return netfs_group; +} + +/* + * Dispose of a netfs group attached to a dirty page (e.g. a ceph snap). + */ +static inline void netfs_put_group(struct netfs_group *netfs_group) +{ + if (netfs_group && refcount_dec_and_test(&netfs_group->ref)) + netfs_group->free(netfs_group); +} + +/* + * Dispose of a netfs group attached to a dirty page (e.g. a ceph snap). + */ +static inline void netfs_put_group_many(struct netfs_group *netfs_group, int nr) +{ + if (netfs_group && refcount_sub_and_test(nr, &netfs_group->ref)) + netfs_group->free(netfs_group); +} + /* * fscache-cache.c */ diff --git a/fs/netfs/misc.c b/fs/netfs/misc.c index 96014c3d1683..40421ced4cd3 100644 --- a/fs/netfs/misc.c +++ b/fs/netfs/misc.c @@ -177,9 +177,55 @@ EXPORT_SYMBOL(netfs_clear_inode_writeback); */ void netfs_invalidate_folio(struct folio *folio, size_t offset, size_t length) { + struct netfs_folio *finfo = NULL; + size_t flen = folio_size(folio); + _enter("{%lx},%zx,%zx", folio_index(folio), offset, length); folio_wait_fscache(folio); + + if (!folio_test_private(folio)) + return; + + finfo = netfs_folio_info(folio); + + if (offset == 0 && length >= flen) + goto erase_completely; + + if (finfo) { + /* We have a partially uptodate page from a streaming write. */ + unsigned int fstart = finfo->dirty_offset; + unsigned int fend = fstart + finfo->dirty_len; + unsigned int end = offset + length; + + if (offset >= fend) + return; + if (end <= fstart) + return; + if (offset <= fstart && end >= fend) + goto erase_completely; + if (offset <= fstart && end > fstart) + goto reduce_len; + if (offset > fstart && end >= fend) + goto move_start; + /* A partial write was split. The caller has already zeroed + * it, so just absorb the hole. + */ + } + return; + +erase_completely: + netfs_put_group(netfs_folio_group(folio)); + folio_detach_private(folio); + folio_clear_uptodate(folio); + kfree(finfo); + return; +reduce_len: + finfo->dirty_len = offset + length - finfo->dirty_offset; + return; +move_start: + finfo->dirty_len -= offset - finfo->dirty_offset; + finfo->dirty_offset = offset; } EXPORT_SYMBOL(netfs_invalidate_folio); diff --git a/include/linux/netfs.h b/include/linux/netfs.h index a14af93efccf..2406e11b41bd 100644 --- a/include/linux/netfs.h +++ b/include/linux/netfs.h @@ -140,6 +140,47 @@ struct netfs_inode { #define NETFS_ICTX_ODIRECT 0 /* The file has DIO in progress */ }; +/* + * A netfs group - for instance a ceph snap. This is marked on dirty pages and + * pages marked with a group must be flushed before they can be written under + * the domain of another group. + */ +struct netfs_group { + refcount_t ref; + void (*free)(struct netfs_group *netfs_group); +}; + +/* + * Information about a dirty page (attached only if necessary). + * folio->private + */ +struct netfs_folio { + struct netfs_group *netfs_group; /* Filesystem's grouping marker (or NULL). */ + unsigned int dirty_offset; /* Write-streaming dirty data offset */ + unsigned int dirty_len; /* Write-streaming dirty data length */ +}; +#define NETFS_FOLIO_INFO 0x1UL /* OR'd with folio->private. */ + +static inline struct netfs_folio *netfs_folio_info(struct folio *folio) +{ + void *priv = folio_get_private(folio); + + if ((unsigned long)priv & NETFS_FOLIO_INFO) + return (struct netfs_folio *)((unsigned long)priv & ~NETFS_FOLIO_INFO); + return NULL; +} + +static inline struct netfs_group *netfs_folio_group(struct folio *folio) +{ + struct netfs_folio *finfo; + void *priv = folio_get_private(folio); + + finfo = netfs_folio_info(folio); + if (finfo) + return finfo->netfs_group; + return priv; +} + /* * Resources required to do operations on a cache. */