From mboxrd@z Thu Jan 1 00:00:00 1970 From: Tyler Hicks Subject: Re: [PATCH] vfs: Export fallocate facility to kernel modules Date: Sat, 5 Nov 2011 08:30:02 -0400 Message-ID: <20111105123001.GA23778@boyd> References: <1320088445-12373-1-git-send-email-thieule@chromium.org> Mime-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha512; protocol="application/pgp-signature"; boundary="wac7ysb48OaltWcw" Cc: viro@zeniv.linux.org.uk, Christoph Hellwig , linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org To: Thieu Le Return-path: Content-Disposition: inline In-Reply-To: <1320088445-12373-1-git-send-email-thieule@chromium.org> Sender: linux-kernel-owner@vger.kernel.org List-Id: linux-fsdevel.vger.kernel.org --wac7ysb48OaltWcw Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On 2011-10-31 12:14:05, Thieu Le wrote: > Export fallocate facility so layered file systems such as ecryptfs can > take advantage of this feature. One example of the need for fallocate > is by ecryptfs. ecryptfs has recently switched to a writeback cache > model so its dirty pages are not written to the lower file system > immediately. In order to ensure that space is available when the page > is later written, ecryptfs can efficiently preallocate that space using > vfs_fallocate(). Hi Thieu - Thanks for the patch. Something like this is definitely needed for eCryptfs. >=20 > vfs_fallocate() does not perform all of the checkings of do_fallocate() > because those checks are done higher in the stack. After taking a closer look at the checks in do_fallocate(), I don't know that this statement is correct. The sanity checks around offset, len, and mode aren't guaranteed to be done higher up in the stack. The existing VFS helper functions also seem to do these types of checks. I think the rest of the checks are redundant. Tyler > Checking of offset and > len are done by rw_verify_area() and generic_write_checks(). These > functions are called by VFS before ecryptfs invokes vfs_fallocate() in its > ecryptfs_write_end() function. And since ecryptfs directly opens the low= er > file, it ensures that the file is opened with the proper flags and mode. >=20 > Signed-off-by: Thieu Le > --- > fs/open.c | 14 ++++++++++---- > include/linux/fs.h | 2 ++ > 2 files changed, 12 insertions(+), 4 deletions(-) >=20 > diff --git a/fs/open.c b/fs/open.c > index f711921..8a4ba20 100644 > --- a/fs/open.c > +++ b/fs/open.c > @@ -214,6 +214,15 @@ SYSCALL_ALIAS(sys_ftruncate64, SyS_ftruncate64); > #endif /* BITS_PER_LONG =3D=3D 32 */ > =20 > =20 > +int vfs_fallocate(struct file *file, int mode, loff_t offset, loff_t len) > +{ > + if (!file->f_op->fallocate) > + return -EOPNOTSUPP; > + > + return file->f_op->fallocate(file, mode, offset, len); > +} > +EXPORT_SYMBOL(vfs_fallocate); > + > int do_fallocate(struct file *file, int mode, loff_t offset, loff_t len) > { > struct inode *inode =3D file->f_path.dentry->d_inode; > @@ -263,10 +272,7 @@ int do_fallocate(struct file *file, int mode, loff_t= offset, loff_t len) > if (((offset + len) > inode->i_sb->s_maxbytes) || ((offset + len) < 0)) > return -EFBIG; > =20 > - if (!file->f_op->fallocate) > - return -EOPNOTSUPP; > - > - return file->f_op->fallocate(file, mode, offset, len); > + return vfs_fallocate(file, mode, offset, len); > } > =20 > SYSCALL_DEFINE(fallocate)(int fd, int mode, loff_t offset, loff_t len) > diff --git a/include/linux/fs.h b/include/linux/fs.h > index 277f497..c0e1225 100644 > --- a/include/linux/fs.h > +++ b/include/linux/fs.h > @@ -1504,6 +1504,8 @@ extern int vfs_link(struct dentry *, struct inode *= , struct dentry *); > extern int vfs_rmdir(struct inode *, struct dentry *); > extern int vfs_unlink(struct inode *, struct dentry *); > extern int vfs_rename(struct inode *, struct dentry *, struct inode *, s= truct dentry *); > +extern int vfs_fallocate(struct file *file, int mode, loff_t offset, > + loff_t len); > =20 > /* > * VFS dentry helper functions. > --=20 > 1.7.3.1 >=20 > -- > To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" = in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html --wac7ysb48OaltWcw Content-Type: application/pgp-signature; name="signature.asc" Content-Description: Digital signature -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.11 (GNU/Linux) iQIcBAEBCgAGBQJOtSxJAAoJENaSAD2qAscKQ/cP/RjZWDBzYaIIibS7N8FxCFyA hKI0t6WD2E5Sf7oGaMSnGwOZ2+NjAZR61juaGHpp7UKJEy6HUTCkElcyxfX8L+OM uzlSOtEGn3mL7HcF9apxbgHaqzqi6t44niiyRM+wbOlqw3HknK18p/0pV2QUc65N opb8iG8ElRRq/+WHznAWxsdmOBbg2AMGMgPu5s25PaAaUiy7DKabpY5WHsmORK8E yd8ljPkHhTc25lkZ2zotRnU7zcef339BqaG0nL33yi9hdWPf6iZ6iyDtJt53MDdP lFtGCHMf15xwXgmn7TF/m8LNzRewKlllP858PPAZQa0HJQxj47W3HVs86OdfukbZ p+O3aSFaBykos17qwEfzWVMiLkQ1VQVCjeenB5qNBa2IG8xt3PAkoT69f5nAWoIO fmQlHMBCTsqyRNRQTdh0J0ze3+9Q7BLvwpWAw0iHBTqwgiOf1fEBo0VTE090QyQF OqRWVnC/hRFdSsqdhL1EbM6b6PfQ8g8z8exa4kazBBuFYHNpMV7wl7qbNCLOPXfY 1rJQyEbXb89MmisbVvE68T7kWZMixARtdKR4VfW4Xo5m0OhMU30d3rDYqFioZc0s 5jrrpl5wI8866uocWjJuBn9y7I+0gGvlL2a4vSnGneEs7o3l5A5KZINNlJMtJ22X 5vuupLuz63t1S93c28nU =NYDf -----END PGP SIGNATURE----- --wac7ysb48OaltWcw--