afs: Fix EOF corruption
[ Upstream commit3f4aa98181
] When doing a partial writeback, afs_write_back_from_locked_page() may generate an FS.StoreData RPC request that writes out part of a file when a file has been constructed from pieces by doing seek, write, seek, write, ... as is done by ld. The FS.StoreData RPC is given the current i_size as the file length, but the server basically ignores it unless the data length is 0 (in which case it's just a truncate operation). The revised file length returned in the result of the RPC may then not reflect what we suggested - and this leads to i_size getting moved backwards - which causes issues later. Fix the client to take account of this by ignoring the returned file size unless the data version number jumped unexpectedly - in which case we're going to have to clear the pagecache and reload anyway. This can be observed when doing a kernel build on an AFS mount. The following pair of commands produce the issue: ld -m elf_x86_64 -z max-page-size=0x200000 --emit-relocs \ -T arch/x86/realmode/rm/realmode.lds \ arch/x86/realmode/rm/header.o \ arch/x86/realmode/rm/trampoline_64.o \ arch/x86/realmode/rm/stack.o \ arch/x86/realmode/rm/reboot.o \ -o arch/x86/realmode/rm/realmode.elf arch/x86/tools/relocs --realmode \ arch/x86/realmode/rm/realmode.elf \ >arch/x86/realmode/rm/realmode.relocs This results in the latter giving: Cannot read ELF section headers 0/18: Success as the realmode.elf file got corrupted. The sequence of events can also be driven with: xfs_io -t -f \ -c "pwrite -S 0x58 0 0x58" \ -c "pwrite -S 0x59 10000 1000" \ -c "close" \ /afs/example.com/scratch/a Fixes:31143d5d51
("AFS: implement basic file write support") Signed-off-by: David Howells <dhowells@redhat.com> Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
parent
c8c19fcdab
commit
4fd68a35f6
|
@ -171,6 +171,7 @@ static void afs_apply_status(struct afs_fs_cursor *fc,
|
|||
struct timespec64 t;
|
||||
umode_t mode;
|
||||
bool data_changed = false;
|
||||
bool change_size = false;
|
||||
|
||||
BUG_ON(test_bit(AFS_VNODE_UNSET, &vnode->flags));
|
||||
|
||||
|
@ -226,6 +227,7 @@ static void afs_apply_status(struct afs_fs_cursor *fc,
|
|||
} else {
|
||||
set_bit(AFS_VNODE_ZAP_DATA, &vnode->flags);
|
||||
}
|
||||
change_size = true;
|
||||
} else if (vnode->status.type == AFS_FTYPE_DIR) {
|
||||
/* Expected directory change is handled elsewhere so
|
||||
* that we can locally edit the directory and save on a
|
||||
|
@ -233,11 +235,19 @@ static void afs_apply_status(struct afs_fs_cursor *fc,
|
|||
*/
|
||||
if (test_bit(AFS_VNODE_DIR_VALID, &vnode->flags))
|
||||
data_changed = false;
|
||||
change_size = true;
|
||||
}
|
||||
|
||||
if (data_changed) {
|
||||
inode_set_iversion_raw(&vnode->vfs_inode, status->data_version);
|
||||
afs_set_i_size(vnode, status->size);
|
||||
|
||||
/* Only update the size if the data version jumped. If the
|
||||
* file is being modified locally, then we might have our own
|
||||
* idea of what the size should be that's not the same as
|
||||
* what's on the server.
|
||||
*/
|
||||
if (change_size)
|
||||
afs_set_i_size(vnode, status->size);
|
||||
}
|
||||
}
|
||||
|
||||
|
|
Loading…
Reference in New Issue