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ca9ca1a5 |
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29-Jan-2024 |
David Howells <dhowells@redhat.com> |
netfs: Fix missing zero-length check in unbuffered write Fix netfs_unbuffered_write_iter() to return immediately if generic_write_checks() returns 0, indicating there's nothing to write. Note that netfs_file_write_iter() already does this. Also, whilst we're at it, put in checks for the size being zero before we even take the locks. Note that generic_write_checks() can still reduce the size to zero, so we still need that check. Without this, a warning similar to the following is logged to dmesg: netfs: Zero-sized write [R=1b6da] and the syscall fails with EIO, e.g.: /sbin/ldconfig.real: Writing of cache extension data failed: Input/output error This can be reproduced on 9p by: xfs_io -f -c 'pwrite 0 0' /xfstest.test/foo Fixes: 153a9961b551 ("netfs: Implement unbuffered/DIO write support") Reported-by: Eric Van Hensbergen <ericvh@kernel.org> Link: https://lore.kernel.org/r/ZbQUU6QKmIftKsmo@FV7GG9FTHL/ Signed-off-by: David Howells <dhowells@redhat.com> Link: https://lore.kernel.org/r/20240129094924.1221977-3-dhowells@redhat.com Tested-by: Dominique Martinet <asmadeus@codewreck.org> Reviewed-by: Jeff Layton <jlayton@kernel.org> cc: Dominique Martinet <asmadeus@codewreck.org> cc: Jeff Layton <jlayton@kernel.org> cc: <v9fs@lists.linux.dev> cc: <linux_oss@crudebyte.com> cc: <netfs@lists.linux.dev> cc: <linux-fsdevel@vger.kernel.org> Signed-off-by: Christian Brauner <brauner@kernel.org>
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100ccd18 |
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24-Nov-2023 |
David Howells <dhowells@redhat.com> |
netfs: Optimise away reads above the point at which there can be no data Track the file position above which the server is not expected to have any data (the "zero point") and preemptively assume that we can satisfy requests by filling them with zeroes locally rather than attempting to download them if they're over that line - even if we've written data back to the server. Assume that any data that was written back above that position is held in the local cache. Note that we have to split requests that straddle the line. Make use of this to optimise away some reads from the server. We need to set the zero point in the following circumstances: (1) When we see an extant remote inode and have no cache for it, we set the zero_point to i_size. (2) On local inode creation, we set zero_point to 0. (3) On local truncation down, we reduce zero_point to the new i_size if the new i_size is lower. (4) On local truncation up, we don't change zero_point. (5) On local modification, we don't change zero_point. (6) On remote invalidation, we set zero_point to the new i_size. (7) If stored data is discarded from the pagecache or culled from fscache, we must set zero_point above that if the data also got written to the server. (8) If dirty data is written back to the server, but not fscache, we must set zero_point above that. (9) If a direct I/O write is made, set zero_point above that. Assuming the above, any read from the server at or above the zero_point position will return all zeroes. The zero_point value can be stored in the cache, provided the above rules are applied to it by any code that culls part of the local cache. Signed-off-by: David Howells <dhowells@redhat.com> cc: Jeff Layton <jlayton@kernel.org> cc: linux-cachefs@redhat.com cc: linux-fsdevel@vger.kernel.org cc: linux-mm@kvack.org
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153a9961 |
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21-Feb-2022 |
David Howells <dhowells@redhat.com> |
netfs: Implement unbuffered/DIO write support Implement support for unbuffered writes and direct I/O writes. If the write is misaligned with respect to the fscrypt block size, then RMW cycles are performed if necessary. DIO writes are a special case of unbuffered writes with extra restriction imposed, such as block size alignment requirements. Also provide a field that can tell the code to add some extra space onto the bounce buffer for use by the filesystem in the case of a content-encrypted file. Signed-off-by: David Howells <dhowells@redhat.com> Reviewed-by: Jeff Layton <jlayton@kernel.org> cc: linux-cachefs@redhat.com cc: linux-fsdevel@vger.kernel.org cc: linux-mm@kvack.org
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