linux/fs/cachefiles/internal.h

408 lines
12 KiB

cachefiles: Implement backing file wrangling Implement the wrangling of backing files, including the following pieces: (1) Lookup and creation of a file on disk, using a tmpfile if the file isn't yet present. The file is then opened, sized for DIO and the file handle is attached to the cachefiles_object struct. The inode is marked to indicate that it's in use by a kernel service. (2) Invalidation of an object, creating a tmpfile and switching the file pointer in the cachefiles object. (3) Committing a file to disk, including setting the coherency xattr on it and, if necessary, creating a hard link to it. Note that this would be a good place to use Omar Sandoval's vfs_link() with AT_LINK_REPLACE[1] as I may have to unlink an old file before I can link a tmpfile into place. (4) Withdrawal of open objects when a cache is being withdrawn or a cookie is relinquished. This involves committing or discarding the file. Changes ======= ver #2: - Fix logging of wrong error[1]. Signed-off-by: David Howells <dhowells@redhat.com> Reviewed-by: Jeff Layton <jlayton@kernel.org> cc: linux-cachefs@redhat.com Link: https://lore.kernel.org/r/20211203094950.GA2480@kili/ [1] Link: https://lore.kernel.org/r/163819644097.215744.4505389616742411239.stgit@warthog.procyon.org.uk/ # v1 Link: https://lore.kernel.org/r/163906949512.143852.14222856795032602080.stgit@warthog.procyon.org.uk/ # v2 Link: https://lore.kernel.org/r/163967158526.1823006.17482695321424642675.stgit@warthog.procyon.org.uk/ # v3 Link: https://lore.kernel.org/r/164021557060.640689.16373541458119269871.stgit@warthog.procyon.org.uk/ # v4
2021-10-21 08:50:10 +01:00
cachefiles: Implement backing file wrangling Implement the wrangling of backing files, including the following pieces: (1) Lookup and creation of a file on disk, using a tmpfile if the file isn't yet present. The file is then opened, sized for DIO and the file handle is attached to the cachefiles_object struct. The inode is marked to indicate that it's in use by a kernel service. (2) Invalidation of an object, creating a tmpfile and switching the file pointer in the cachefiles object. (3) Committing a file to disk, including setting the coherency xattr on it and, if necessary, creating a hard link to it. Note that this would be a good place to use Omar Sandoval's vfs_link() with AT_LINK_REPLACE[1] as I may have to unlink an old file before I can link a tmpfile into place. (4) Withdrawal of open objects when a cache is being withdrawn or a cookie is relinquished. This involves committing or discarding the file. Changes ======= ver #2: - Fix logging of wrong error[1]. Signed-off-by: David Howells <dhowells@redhat.com> Reviewed-by: Jeff Layton <jlayton@kernel.org> cc: linux-cachefs@redhat.com Link: https://lore.kernel.org/r/20211203094950.GA2480@kili/ [1] Link: https://lore.kernel.org/r/163819644097.215744.4505389616742411239.stgit@warthog.procyon.org.uk/ # v1 Link: https://lore.kernel.org/r/163906949512.143852.14222856795032602080.stgit@warthog.procyon.org.uk/ # v2 Link: https://lore.kernel.org/r/163967158526.1823006.17482695321424642675.stgit@warthog.procyon.org.uk/ # v3 Link: https://lore.kernel.org/r/164021557060.640689.16373541458119269871.stgit@warthog.procyon.org.uk/ # v4
2021-10-21 08:50:10 +01:00
cachefiles: Implement key to filename encoding Implement a function to encode a binary cookie key as something that can be used as a filename. Four options are considered: (1) All printable chars with no '/' characters. Prepend a 'D' to indicate the encoding but otherwise use as-is. (2) Appears to be an array of __be32. Encode as 'S' plus a list of hex-encoded 32-bit ints separated by commas. If a number is 0, it is rendered as "" instead of "0". (3) Appears to be an array of __le32. Encoded as (2) but with a 'T' encoding prefix. (4) Encoded as base64 with an 'E' prefix plus a second char indicating how much padding is involved. A non-standard base64 encoding is used because '/' cannot be used in the encoded form. If (1) is not possible, whichever of (2), (3) or (4) produces the shortest string is selected (hex-encoding a number may be less dense than base64 encoding it). Note that the prefix characters have to be selected from the set [DEIJST@] lest cachefilesd remove the files because it recognise the name. Changes ======= ver #2: - Fix a short allocation that didn't allow for a string terminator[1] Signed-off-by: David Howells <dhowells@redhat.com> Reviewed-by: Jeff Layton <jlayton@kernel.org> cc: linux-cachefs@redhat.com Link: https://lore.kernel.org/r/bcefb8f2-576a-b3fc-cc29-89808ebfd7c1@linux.alibaba.com/ [1] Link: https://lore.kernel.org/r/163819640393.215744.15212364106412961104.stgit@warthog.procyon.org.uk/ # v1 Link: https://lore.kernel.org/r/163906940529.143852.17352132319136117053.stgit@warthog.procyon.org.uk/ # v2 Link: https://lore.kernel.org/r/163967149827.1823006.6088580775428487961.stgit@warthog.procyon.org.uk/ # v3 Link: https://lore.kernel.org/r/164021549223.640689.14762875188193982341.stgit@warthog.procyon.org.uk/ # v4
2021-11-17 15:48:06 +00:00
cachefiles: Implement backing file wrangling Implement the wrangling of backing files, including the following pieces: (1) Lookup and creation of a file on disk, using a tmpfile if the file isn't yet present. The file is then opened, sized for DIO and the file handle is attached to the cachefiles_object struct. The inode is marked to indicate that it's in use by a kernel service. (2) Invalidation of an object, creating a tmpfile and switching the file pointer in the cachefiles object. (3) Committing a file to disk, including setting the coherency xattr on it and, if necessary, creating a hard link to it. Note that this would be a good place to use Omar Sandoval's vfs_link() with AT_LINK_REPLACE[1] as I may have to unlink an old file before I can link a tmpfile into place. (4) Withdrawal of open objects when a cache is being withdrawn or a cookie is relinquished. This involves committing or discarding the file. Changes ======= ver #2: - Fix logging of wrong error[1]. Signed-off-by: David Howells <dhowells@redhat.com> Reviewed-by: Jeff Layton <jlayton@kernel.org> cc: linux-cachefs@redhat.com Link: https://lore.kernel.org/r/20211203094950.GA2480@kili/ [1] Link: https://lore.kernel.org/r/163819644097.215744.4505389616742411239.stgit@warthog.procyon.org.uk/ # v1 Link: https://lore.kernel.org/r/163906949512.143852.14222856795032602080.stgit@warthog.procyon.org.uk/ # v2 Link: https://lore.kernel.org/r/163967158526.1823006.17482695321424642675.stgit@warthog.procyon.org.uk/ # v3 Link: https://lore.kernel.org/r/164021557060.640689.16373541458119269871.stgit@warthog.procyon.org.uk/ # v4
2021-10-21 08:50:10 +01:00
cachefiles: Implement backing file wrangling Implement the wrangling of backing files, including the following pieces: (1) Lookup and creation of a file on disk, using a tmpfile if the file isn't yet present. The file is then opened, sized for DIO and the file handle is attached to the cachefiles_object struct. The inode is marked to indicate that it's in use by a kernel service. (2) Invalidation of an object, creating a tmpfile and switching the file pointer in the cachefiles object. (3) Committing a file to disk, including setting the coherency xattr on it and, if necessary, creating a hard link to it. Note that this would be a good place to use Omar Sandoval's vfs_link() with AT_LINK_REPLACE[1] as I may have to unlink an old file before I can link a tmpfile into place. (4) Withdrawal of open objects when a cache is being withdrawn or a cookie is relinquished. This involves committing or discarding the file. Changes ======= ver #2: - Fix logging of wrong error[1]. Signed-off-by: David Howells <dhowells@redhat.com> Reviewed-by: Jeff Layton <jlayton@kernel.org> cc: linux-cachefs@redhat.com Link: https://lore.kernel.org/r/20211203094950.GA2480@kili/ [1] Link: https://lore.kernel.org/r/163819644097.215744.4505389616742411239.stgit@warthog.procyon.org.uk/ # v1 Link: https://lore.kernel.org/r/163906949512.143852.14222856795032602080.stgit@warthog.procyon.org.uk/ # v2 Link: https://lore.kernel.org/r/163967158526.1823006.17482695321424642675.stgit@warthog.procyon.org.uk/ # v3 Link: https://lore.kernel.org/r/164021557060.640689.16373541458119269871.stgit@warthog.procyon.org.uk/ # v4
2021-10-21 08:50:10 +01:00